Symbolic Expressions

RELATIONAL EXPRESSIONS:

We create a relational expression:

sage: x = var('x')
sage: eqn = (x-1)^2 <= x^2 - 2*x + 3
sage: eqn.subs(x == 5)
16 <= 18

Notice that squaring the relation squares both sides.

sage: eqn^2
(x - 1)^4 <= (x^2 - 2*x + 3)^2
sage: eqn.expand()
x^2 - 2*x + 1 <= x^2 - 2*x + 3

The can transform a true relational into a false one:

sage: eqn = SR(-5) < SR(-3); eqn
-5 < -3
sage: bool(eqn)
True
sage: eqn^2
25 < 9
sage: bool(eqn^2)
False

We can do arithmetic with relationals:

sage: e = x+1 <= x-2
sage: e + 2
x + 3 <= x
sage: e - 1
x <= x - 3
sage: e*(-1)
-x - 1 <= -x + 2
sage: (-2)*e
-2*x - 2 <= -2*x + 4
sage: e*5
5*x + 5 <= 5*x - 10
sage: e/5
1/5*x + 1/5 <= 1/5*x - 2/5
sage: 5/e
5/(x + 1) <= 5/(x - 2)
sage: e/(-2)
-1/2*x - 1/2 <= -1/2*x + 1
sage: -2/e
-2/(x + 1) <= -2/(x - 2)

We can even add together two relations, so long as the operators are the same:

sage: (x^3 + x <= x - 17)  + (-x <= x - 10)
x^3 <= 2*x - 27

Here they aren’t:

sage: (x^3 + x <= x - 17)  + (-x >= x - 10)
...
TypeError: incompatible relations

ARBITRARY SAGE ELEMENTS:

You can work symbolically with any Sage data type. This can lead to nonsense if the data type is strange, e.g., an element of a finite field (at present).

We mix Singular variables with symbolic variables:

sage: R.<u,v> = QQ[]
sage: var('a,b,c')
(a, b, c)
sage: expand((u + v + a + b + c)^2)
a^2 + 2*a*b + 2*a*c + 2*a*u + 2*a*v + b^2 + 2*b*c + 2*b*u + 2*b*v + c^2 + 2*c*u + 2*c*v + u^2 + 2*u*v + v^2

TESTS:

Test Jacobian on Pynac expressions. #5546

sage: var('x,y')
(x, y)
sage: f = x + y
sage: jacobian(f, [x,y])
[1 1]

Test if matrices work #5546

sage: var('x,y,z')
(x, y, z)
sage: M = matrix(2,2,[x,y,z,x])
sage: v = vector([x,y])
sage: M * v
(x^2 + y^2, x*y + x*z)
sage: v*M
(x^2 + y*z, 2*x*y)

Test if comparison bugs from #6256 are fixed:

sage: t = exp(sqrt(x)); u = 1/t
sage: t*u
1
sage: t + u
e^sqrt(x) + e^(-sqrt(x))
sage: t
e^sqrt(x)
class sage.symbolic.expression.Expression
Order()

Order, as in big oh notation.

OUTPUT:
symbolic expression
EXAMPLES:
sage: n = var(‘n’) sage: (17*n^3).Order() Order(n^3)
__abs__()

Return the absolute value of this expression.

EXAMPLES:

sage: var('x, y')
(x, y)

The absolute value of a symbolic expression:

sage: abs(x^2+y^2)
abs(x^2 + y^2)

The absolute value of a number in the symbolic ring:

sage: abs(SR(-5))
5
sage: type(abs(SR(-5)))
<type 'sage.symbolic.expression.Expression'>
__call__()

Calls the subs() on this expression.

EXAMPLES:

sage: var('x,y,z')
(x, y, z)
sage: (x+y)(x=z^2, y=x^y)
x^y + z^2
__cmp__()
x.__cmp__(y) <==> cmp(x,y)
__complex__()

EXAMPLES:

sage: complex(I)
1j
sage: complex(erf(3*I))
...
TypeError: unable to simplify to complex approximation
__eq__()
x.__eq__(y) <==> x==y
__float__()

Return float conversion of self, assuming self is constant. Otherwise, raise a TypeError.

OUTPUT:

  • float - double precision evaluation of self

EXAMPLES:

sage: float(SR(12))
12.0
sage: float(SR(2/3))
0.66666666666666663
sage: float(sqrt(SR(2)))
1.4142135623730951
sage: float(x^2 + 1)
...
TypeError: float() argument must be a string or a number
sage: float(SR(RIF(2)))
...
TypeError: a float is required
__ge__()
x.__ge__(y) <==> x>=y
__getstate__()

Returns a tuple describing the state of this expression for pickling.

This should return all information that will be required to unpickle the object. The functionality for unpickling is implemented in __setstate__().

In order to pickle Expression objects, we return a tuple containing

  • 0 - as pickle version number

    in case we decide to change the pickle format in the feature

  • names of symbols of this expression

  • a string representation of self stored in a Pynac archive.

TESTS::

sage: var(‘x,y,z’) (x, y, z) sage: t = 2*x*y^z+3 sage: s = dumps(t)

sage: t.__getstate__() (0,

[‘x’, ‘y’, ‘z’], ...)
__gt__()
x.__gt__(y) <==> x>y
__hash__()
x.__hash__() <==> hash(x)
__index__()

EXAMPLES:

sage: a = range(10)
sage: a[:SR(5)]
[0, 1, 2, 3, 4]
__init__()
x.__init__(...) initializes x; see x.__class__.__doc__ for signature
__int__()

EXAMPLES:

sage: int(sin(2)*100)
90
sage: int(log(8)/log(2))
3
__invert__()

Return the inverse of this symbolic expression.

EXAMPLES:

sage: ~x
1/x
sage: ~SR(3)
1/3
sage: v1=var('v1'); a = (2*erf(2*v1*arcsech(0))/v1); ~a
1/2*v1/erf(2*v1*arcsech(0))
__le__()
x.__le__(y) <==> x<=y
__len__()
x.__len__() <==> len(x)
__long__()

EXAMPLES:

sage: long(sin(2)*100)
90L
__lt__()
x.__lt__(y) <==> x<y
__ne__()
x.__ne__(y) <==> x!=y
static __new__()
T.__new__(S, ...) -> a new object with type S, a subtype of T
__nonzero__()
x.__nonzero__() <==> x != 0
__pow__()
x.__pow__(y[, z]) <==> pow(x, y[, z])
__rpow__()
y.__rpow__(x[, z]) <==> pow(x, y[, z])
__setstate__()

Initializes the state of the object from data saved in a pickle.

During unpickling __init__ methods of classes are not called, the saved data is passed to the class via this function instead.

TESTS::

sage: var(‘x,y,z’) (x, y, z) sage: t = 2*x*y^z+3 sage: u = loads(dumps(t)) # indirect doctest sage: u 2*y^z*x + 3 sage: bool(t == u) True sage: u.subs(x=z) 2*y^z*z + 3

sage: loads(dumps(x.parent()(2))) 2

_add_()

Add left and right.

EXAMPLES:

sage: var("x y")
(x, y)
sage: x + y + y + x
2*x + 2*y

# adding relational expressions
sage: ( (x+y) > x ) + ( x > y )
2*x + y > x + y

sage: ( (x+y) > x ) + x
2*x + y > 2*x

TESTS:

sage: x + ( (x+y) > x )
2*x + y > 2*x

sage: ( x > y) + (y < x)
...
TypeError: incompatible relations

sage: (x < 1) + (y <= 2)
x + y < 3

sage: x + oo
+Infinity
sage: x - oo
-Infinity
sage: x + unsigned_infinity
Infinity
sage: x - unsigned_infinity
Infinity

sage: nsr = x.parent()
sage: nsr(oo) + nsr(oo)
+Infinity
sage: nsr(-oo) + nsr(-oo)
-Infinity
sage: nsr(oo) - nsr(oo)
...
RuntimeError: indeterminate expression: Infinity - Infinity encountered.
sage: nsr(-oo) - nsr(-oo)
...
RuntimeError: indeterminate expression: Infinity - Infinity encountered.

sage: nsr(unsigned_infinity) + nsr(oo)
...
RuntimeError: indeterminate expression: unsigned_infinity + x where x is Infinity, -Infinity or unsigned infinity encountered.
sage: nsr(unsigned_infinity) - nsr(oo)
...
RuntimeError: indeterminate expression: unsigned_infinity + x where x is Infinity, -Infinity or unsigned infinity encountered.
sage: nsr(oo) + nsr(unsigned_infinity)
...
RuntimeError: indeterminate expression: unsigned_infinity + x where x is Infinity, -Infinity or unsigned infinity encountered.
sage: nsr(oo) - nsr(unsigned_infinity)
...
RuntimeError: indeterminate expression: unsigned_infinity + x where x is Infinity, -Infinity or unsigned infinity encountered.
sage: nsr(unsigned_infinity) + nsr(unsigned_infinity)
...
RuntimeError: indeterminate expression: unsigned_infinity + x where x is Infinity, -Infinity or unsigned infinity encountered.
_algebraic_()

Convert a symbolic expression to an algebraic number.

EXAMPLES:

sage: QQbar(sqrt(2) + sqrt(8))
4.242640687119285?
sage: AA(sqrt(2) ^ 4) == 4
True
sage: AA(-golden_ratio)
-1.618033988749895?
sage: QQbar((2*I)^(1/2))
1 + 1*I
sage: QQbar(e^(pi*I/3))
0.500000000000000? + 0.866025403784439?*I

sage: QQbar(sqrt(2))
1.414213562373095?
sage: AA(abs(1+I))
1.414213562373095?
sage: golden_ratio._algebraic_(QQbar)
1.618033988749895?
sage: QQbar(golden_ratio)
1.618033988749895?

sage: AA(x*sin(0))
0
sage: QQbar(x*sin(0))
0
_complex_double_()

Return a numerical approximation to this expression in the given Complex Double Field R.

EXAMPLES:

sage: CDF(SR(1/11)) 
0.0909090909091
sage: zeta(x).subs(x=I)._complex_double_(CDF)
0.00330022368532 - 0.418155449141*I
sage: gamma(x).subs(x=I)._complex_double_(CDF)
-0.154949828302 - 0.498015668118*I
sage: log(x).subs(x=I)._complex_double_(CDF)
1.57079632679*I
sage: CDF((-1)^(1/3))
0.5 + 0.866025403784*I
_complex_mpfi_()

Returns this expression as a complex interval.

EXAMPLES:

sage: CIF(pi)
3.141592653589794?
_complex_mpfr_field_()

Return a numerical approximation to this expression in the given ComplexField R.

The precision of the approximation is determined by the precision of the input R.

EXAMPLES:

sage: ComplexField(200)(SR(1/11)) 
0.090909090909090909090909090909090909090909090909090909090909
sage: zeta(x).subs(x=I)._complex_mpfr_field_(ComplexField(70))
0.0033002236853241028742 - 0.41815544914132167669*I
sage: gamma(x).subs(x=I)._complex_mpfr_field_(ComplexField(60))
-0.15494982830181069 - 0.49801566811835604*I
sage: log(x).subs(x=I)._complex_mpfr_field_(ComplexField(50))
1.5707963267949*I

sage: CC(sqrt(2))
1.41421356237310
sage: a = sqrt(-2); a
sqrt(-2)
sage: CC(a).imag()
1.41421356237309
sage: ComplexField(200)(a).imag()
1.4142135623730950488016887242096980785696718753769480731767
sage: ComplexField(100)((-1)^(1/10))
0.95105651629515357211643933338 + 0.30901699437494742410229341718*I
sage: CC(x*sin(0))
0
_convert()

Convert self to the given type by converting each of the operands to that type and doing the arithmetic.

FIXME: Make sure these docs are correct with the new symbolics.

EXAMPLES:

sage: f = sqrt(2) * cos(3); f
sqrt(2)*cos(3)
sage: f._convert(RDF)
-1.40006081534
sage: f._convert(float)
-1.4000608153399503

Converting to an int can have surprising consequences, since Python int is “floor” and one individual factor can floor to 0 but the product doesn’t:

sage: int(f)
-1
sage: f._convert(int)
0
sage: int(sqrt(2))
1
sage: int(cos(3))
0

TESTS: This illustrates how the conversion works even when a type exception is raised, since here one operand is still x (in the unsimplified form):

sage: f = sin(SR(0))*x
sage: f._convert(CDF)
0
_derivative()

Return the deg-th (partial) derivative of self with respect to symb.

EXAMPLES:

sage: var("x y")
(x, y)
sage: b = (x+y)^5
sage: b._derivative(x, 2)
20*(x + y)^3

sage: from sage.symbolic.function import function as myfunc
sage: foo = myfunc('foo',2)
sage: foo(x^2,x^2)._derivative(x)
2*x*D[0](foo)(x^2, x^2) + 2*x*D[1](foo)(x^2, x^2)

sage: SR(1)._derivative()
0

TESTS:

Raise error if no variable is specified and there are multiple variables:

sage: b._derivative()
...
ValueError: No differentiation variable specified.
_div_()

Divide left and right.

EXAMPLES:

sage: var("x y")
(x, y)
sage: x/y/y
x/y^2

# dividing relational expressions
sage: ( (x+y) > x ) / ( x > y )
(x + y)/x > x/y

sage: ( (x+y) > x ) / x
(x + y)/x > 1

sage: ( (x+y) > x ) / -1
-x - y > -x

TESTS:

sage: x / ( (x+y) > x )
x/(x + y) > 1

sage: ( x > y) / (y < x)
...
TypeError: incompatible relations
sage: x/oo
0
sage: oo/x
+Infinity

sage: SR(oo)/SR(oo)
...
RuntimeError: indeterminate expression: 0*infinity encountered.

sage: SR(-oo)/SR(oo)
...
RuntimeError: indeterminate expression: 0*infinity encountered.

sage: SR(oo)/SR(-oo)
...
RuntimeError: indeterminate expression: 0*infinity encountered.

sage: SR(oo)/SR(unsigned_infinity)
...
RuntimeError: indeterminate expression: 0*infinity encountered.

sage: SR(unsigned_infinity)/SR(oo)
...
RuntimeError: indeterminate expression: 0*infinity encountered.

sage: SR(0)/SR(oo)
0

sage: SR(0)/SR(unsigned_infinity)
0

sage: x/0
...
ZeroDivisionError: Symbolic division by zero
_eval_self()

Evaluate this expression numerically, and try to coerce it to R.

EXAMPLES:

sage: var('x,y,z')
(x, y, z)
sage: sin(x).subs(x=5)._eval_self(RR)
-0.958924274663138
sage: gamma(x).subs(x=I)._eval_self(CC)
-0.154949828301811 - 0.498015668118356*I
sage: x._eval_self(CC)
...
TypeError: Cannot evaluate symbolic expression to a numeric value.
_factor_list()

Turn an expression already in factored form into a list of (prime, power) pairs.

This is used, e.g., internally by the factor_list() command.

EXAMPLES:

sage: g = factor(x^3 - 1); g
(x - 1)*(x^2 + x + 1)
sage: v = g._factor_list(); v
[(x - 1, 1), (x^2 + x + 1, 1)]
sage: type(v)
<type 'list'>
_fast_callable_()

Given an ExpressionTreeBuilder etb, return an Expression representing this symbolic expression.

EXAMPLES:

sage: from sage.ext.fast_callable import ExpressionTreeBuilder
sage: etb = ExpressionTreeBuilder(vars=['x','y'])
sage: x,y = var('x,y')
sage: f = y+2*x^2
sage: f._fast_callable_(etb)
add(mul(ipow(v_0, 2), 2), v_1)
_fast_float_()

Returns an object which provides fast floating point evaluation of this symbolic expression.

See sage.ext.fast_eval for more information.

EXAMPLES:

sage: f = sqrt(x+1)
sage: ff = f._fast_float_('x')
sage: ff(1.0)
1.4142135623730951
sage: type(_)
<type 'float'>
_gap_init_()

Conversion of symbolic object to GAP always results in a GAP string.

EXAMPLES:

sage: gap(e + pi^2 + x^3)
pi^2 + x^3 + e
_integer_()

EXAMPLES:

sage: f = x^3 + 17*x -3
sage: ZZ(f.coeff(x^3))
1
sage: ZZ(f.coeff(x))
17
sage: ZZ(f.coeff(x,0))
-3
sage: type(ZZ(f.coeff(x,0)))
<type 'sage.rings.integer.Integer'>

Coercion is done if necessary:

sage: f = x^3 + 17/1*x
sage: ZZ(f.coeff(x))
17
sage: type(ZZ(f.coeff(x)))
<type 'sage.rings.integer.Integer'>

If the symbolic expression is just a wrapper around an integer, that very same integer is returned:

sage: n = 17; SR(n)._integer_() is n
True
_interface_()

EXAMPLES:

sage: f = sin(e + 2)
sage: f._interface_(sage.calculus.calculus.maxima)
sin(%e+2)           
_interface_init_()

EXAMPLES:

sage: a = (pi + 2).sin()
sage: a._maxima_init_()
'sin((%pi)+(2))'

sage: a = (pi + 2).sin()
sage: a._maple_init_()
'sin((pi)+(2))'

sage: a = (pi + 2).sin()
sage: a._mathematica_init_()
'Sin[(Pi)+(2)]'

sage: f = pi + I*e
sage: f._pari_init_()
'(Pi)+((exp(1))*(I))'
_latex_()

Return string representation of this symbolic expression.

EXAMPLES:

TESTS:

sage: var('x,y,z')
(x, y, z)
sage: latex(y + 3*(x^(-1)))
y + 3 \, \frac{1}{x}
sage: latex(x^(y+z^(1/y)))
x^{z^{\frac{1}{y}} + y}
sage: latex(1/sqrt(x+y))
\frac{1}{\sqrt{x + y}}
sage: latex(sin(x*(z+y)^x))
\sin\left({(y + z)}^{x} x\right)
sage: latex(3/2*(x+y)/z/y)
\frac{3}{2} \, \frac{{(x + y)}}{y z}
sage: latex((2^(x^y)))
2^{x^{y}}
sage: latex(abs(x))
{\left| x \right|}
sage: latex((x*y).conjugate())
\overline{x} \overline{y}

Check spacing of coefficients of mul expressions (#3202):

sage: latex(2*3^x)
2 \, 3^{x}

Powers:

sage: _ = var('A,B,n')
sage: latex((n+A/B)^(n+1))
{(n + \frac{A}{B})}^{n + 1}
sage: latex((A*B)^n)
{(A B)}^{n}
sage: latex((A*B)^(n-1))
{(A B)}^{n - 1}

Powers where the base or exponent is a Python object:

sage: latex((2/3)^x)
\left(\frac{2}{3}\right)^{x}
sage: latex(x^CDF(1,2))
x^{1.0 + 2.0i}
sage: latex((2/3)^(2/3))
\left(\frac{2}{3}\right)^{\frac{2}{3}}
sage: latex((-x)^(1/4))
{(-x)}^{\frac{1}{4}}
sage: k.<a> = GF(9)
sage: latex(SR(a+1)^x)
\left(a + 1\right)^{x}
_magma_init_()

Return string representation in Magma of this symbolic expression.

Since Magma has no notation of symbolic calculus, this simply returns something that evaluates in Magma to a a Magma string.

EXAMPLES:

sage: x = var('x')                      
sage: f = sin(cos(x^2) + log(x))
sage: f._magma_init_(magma)
'"sin(log(x) + cos(x^2))"'
sage: magma(f)                         # optional - magma
sin(cos(x^2) + log(x))
sage: magma(f).Type()                  # optional - magma
MonStgElt
_mathml_()

Returns a MathML representation of this object.

EXAMPLES:

sage: mathml(pi)
<mi>&pi;</mi>
sage: mathml(pi+2)
MATHML version of the string pi + 2
_maxima_()

EXAMPLES:

sage: f = sin(e + 2)
sage: f._maxima_()
sin(%e+2)
sage: _.parent() is sage.calculus.calculus.maxima
True
_maxima_init_assume_()

Return string that when evaluated in Maxima defines the assumption determined by this expression.

EXAMPLES:

sage: f = x+2 > sqrt(3)
sage: f._maxima_init_assume_()
'((x)+(2))>((3/1)^(1/2))'
_mpfr_()

Return a numerical approximation to this expression in the RealField R.

The precision of the approximation is determined by the precision of the input R.

EXAMPLES:

0.090909090909090909090909090909090909090909090909090909090909

sage: a = sin(3); a
sin(3)
sage: RealField(200)(a)
0.14112000805986722210074480280811027984693326425226558415188
sage: a._mpfr_(RealField(100))
0.14112000805986722210074480281
_mul_()

Multiply left and right.

EXAMPLES:

sage: var("x y")
(x, y)
sage: x*y*y
x*y^2

# multiplying relational expressions
sage: ( (x+y) > x ) * ( x > y )
(x + y)*x > x*y

sage: ( (x+y) > x ) * x
(x + y)*x > x^2

sage: ( (x+y) > x ) * -1
-x - y > -x

TESTS:

sage: x * ( (x+y) > x )
(x + y)*x > x^2

sage: ( x > y) * (y < x)
...
TypeError: incompatible relations

sage: a = 1000 + 300*x + x^3 + 30*x^2
sage: a*Mod(1,7)
x^3 + 2*x^2 + 6*x + 6

sage: var('z')
z
sage: 3*(x+y)/z
3*(x + y)/z
sage: (-x+z)*(3*x-3*z)
-3*(x - z)^2

# check if comparison of constant terms in Pynac add objects work
sage: (y-1)*(y-2)
(y - 2)*(y - 1)

Check for simplifications when multiplying instances of exp:

sage: exp(x)*exp(y)
e^(x + y)
sage: exp(x)^2*exp(y)
e^(2*x + y)
sage: x^y*exp(x+y)*exp(-y)
x^y*e^x
sage: x^y*exp(x+y)*(x+y)*(2*x+2*y)*exp(-y)
2*(x + y)^2*x^y*e^x
sage: x^y*exp(x+y)*(x+y)*(2*x+2*y)*exp(-y)*exp(z)^2
2*(x + y)^2*x^y*e^(x + 2*z)
sage: 1/exp(x)
e^(-x)
sage: exp(x)/exp(y)
e^(x - y)
sage: A = exp(I*pi/5)
sage: t = A*A*A*A; t
e^(4/5*I*pi)
sage: t*A
-1
sage: b = -x*A; c = b*b; c
x^2*e^(2/5*I*pi)
sage: u = -t*A; u
1

sage: x*oo
+Infinity
sage: -x*oo
-Infinity
sage: x*unsigned_infinity
...
ValueError: oo times number < oo not defined

sage: SR(oo)*SR(oo)
+Infinity
sage: SR(-oo)*SR(oo)
-Infinity
sage: SR(oo)*SR(-oo)
-Infinity
sage: SR(unsigned_infinity)*SR(oo)
Infinity
_polynomial_()

Coerce this symbolic expression to a polynomial in R.

EXAMPLES:

sage: var('x,y,z,w')
(x, y, z, w)
sage: R = QQ[x,y,z]
sage: R(x^2 + y)
x^2 + y
sage: R = QQ[w]
sage: R(w^3 + w + 1)
w^3 + w + 1
sage: R = GF(7)[z]
sage: R(z^3 + 10*z)
z^3 + 3*z

Note

If the base ring of the polynomial ring is the symbolic ring, then a constant polynomial is always returned.

sage: R = SR[x]
sage: a = R(sqrt(2) + x^3 + y)
sage: a
y + sqrt(2) + x^3
sage: type(a)
<class 'sage.rings.polynomial.polynomial_element_generic.Polynomial_generic_dense_field'>
sage: a.degree()
0

We coerce to a double precision complex polynomial ring:

sage: f = e*x^3 + pi*y^3 + sqrt(2) + I; f
pi*y^3 + x^3*e + sqrt(2) + I
sage: R = CDF[x,y]
sage: R(f)
2.71828182846*x^3 + 3.14159265359*y^3 + 1.41421356237 + 1.0*I

We coerce to a higher-precision polynomial ring

sage: R = ComplexField(100)[x,y]
sage: R(f)
2.7182818284590452353602874714*x^3 + 3.1415926535897932384626433833*y^3 + 1.4142135623730950488016887242 + 1.0000000000000000000000000000*I

This shows that the issue at trac #4246 is fixed (attempting to coerce an expression containing at least one variable that’s not in R raises an error):

sage: x, y = var('x y')
sage: S = PolynomialRing(Integers(4), 1, 'x')
sage: S(x)
x
sage: S(y)
...
TypeError: y is not a variable of Multivariate Polynomial Ring in x over Ring of integers modulo 4
sage: S(x+y)
...
TypeError: y is not a variable of Multivariate Polynomial Ring in x over Ring of integers modulo 4
sage: (x+y)._polynomial_(S)
...
TypeError: y is not a variable of Multivariate Polynomial Ring in x over Ring of integers modulo 4
_rational_()

EXAMPLES:

sage: f = x^3 + 17/1*x - 3/8
sage: QQ(f.coeff(x^2))
0
sage: QQ(f.coeff(x^3))
1
sage: a = QQ(f.coeff(x)); a
17
sage: type(a)
<type 'sage.rings.rational.Rational'>
sage: QQ(f.coeff(x,0))
-3/8

If the symbolic expression is just a wrapper around a rational, that very same rational is returned:

sage: n = 17/1; SR(n)._rational_() is n
True
_real_double_()

EXAMPLES:

sage: RDF(sin(3))
0.14112000806
_real_mpfi_()

Returns this expression as a real interval.

EXAMPLES:

sage: RIF(sqrt(2))
1.414213562373095?
_repr_()

Return string representation of this symbolic expression.

EXAMPLES:

sage: var("x y")
(x, y)
sage: repr(x+y)
'x + y'

TESTS:

# printing of modular number equal to -1 as coefficient
sage: k.<a> = GF(9); k(2)*x
2*x

sage: (x+1)*Mod(6,7)
6*x + 6

#printing rational functions
sage: x/y
x/y
sage: x/2/y
1/2*x/y
sage: .5*x/y
0.500000000000000*x/y
sage: x^(-1)
1/x
sage: x^(-5)
x^(-5)
sage: x^(-y)
x^(-y)
sage: 2*x^(-1)
2/x
sage: i*x
I*x
sage: -x.parent(i)
-I
sage: y + 3*(x^(-1))
y + 3/x

Printing the exp function:

sage: x.parent(1).exp()
e
sage: x.exp()
e^x

Powers:

sage: _ = var('A,B,n'); (A*B)^n
(A*B)^n
sage: (A/B)^n
(A/B)^n
sage: n*x^(n-1)
n*x^(n - 1)
sage: (A*B)^(n+1)
(A*B)^(n + 1)
sage: (A/B)^(n-1)
(A/B)^(n - 1)
sage: n*x^(n+1)
n*x^(n + 1)
sage: n*x^(n-1)
n*x^(n - 1)
sage: n*(A/B)^(n+1)
n*(A/B)^(n + 1)
sage: (n+A/B)^(n+1)
(n + A/B)^(n + 1)

Powers where the base or exponent is a Python object:

sage: (2/3)^x
(2/3)^x
sage: x^CDF(1,2)
x^(1.0 + 2.0*I)
sage: (2/3)^(2/3)
(2/3)^(2/3)
sage: (-x)^(1/4)
(-x)^(1/4)
sage: k.<a> = GF(9)
sage: SR(a+1)^x
(a + 1)^x
_singular_init_()

Conversion of a symbolic object to Singular always results in a Singular string.

EXAMPLES:

sage: singular(e + pi^2 + x^3)
pi^2 + x^3 + e
_sub_()

EXAMPLES:

sage: var("x y")
(x, y)
sage: x - y
x - y

# subtracting relational expressions
sage: ( (x+y) > x ) - ( x > y )
y > x - y

sage: ( (x+y) > x ) - x
y > 0

TESTS:

sage: x - ( (x+y) > x )
-y > 0

sage: ( x > y) - (y < x)
...
TypeError: incompatible relations

sage: x - oo
-Infinity
sage: oo - x
+Infinity
_subs_expr()

EXAMPLES:

sage: var('x,y,z,a,b,c,d,e,f')
(x, y, z, a, b, c, d, e, f)
sage: w0 = SR.wild(0); w1 = SR.wild(1)
sage: (a^2 + b^2 + (x+y)^2)._subs_expr(w0^2 == w0^3)
(x + y)^3 + a^3 + b^3
sage: (a^4 + b^4 + (x+y)^4)._subs_expr(w0^2 == w0^3)
(x + y)^4 + a^4 + b^4
sage: (a^2 + b^4 + (x+y)^4)._subs_expr(w0^2 == w0^3)
(x + y)^4 + a^3 + b^4
sage: ((a+b+c)^2)._subs_expr(a+b == x)
(a + b + c)^2
sage: ((a+b+c)^2)._subs_expr(a+b+w0 == x+w0)
(c + x)^2
sage: (a+2*b)._subs_expr(a+b == x)
a + 2*b
sage: (a+2*b)._subs_expr(a+b+w0 == x+w0)
a + 2*b
sage: (a+2*b)._subs_expr(a+w0*b == x)
x
sage: (a+2*b)._subs_expr(a+b+w0*b == x+w0*b)
a + 2*b
sage: (4*x^3-2*x^2+5*x-1)._subs_expr(x==a)
4*a^3 - 2*a^2 + 5*a - 1
sage: (4*x^3-2*x^2+5*x-1)._subs_expr(x^w0==a^w0)
4*a^3 - 2*a^2 + 5*x - 1
sage: (4*x^3-2*x^2+5*x-1)._subs_expr(x^w0==a^(2*w0))._subs_expr(x==a)
4*a^6 - 2*a^4 + 5*a - 1
sage: sin(1+sin(x))._subs_expr(sin(w0)==cos(w0))
cos(cos(x) + 1)
sage: (sin(x)^2 + cos(x)^2)._subs_expr(sin(w0)^2+cos(w0)^2==1)
1
sage: (1 + sin(x)^2 + cos(x)^2)._subs_expr(sin(w0)^2+cos(w0)^2==1)
sin(x)^2 + cos(x)^2 + 1
sage: (17*x + sin(x)^2 + cos(x)^2)._subs_expr(w1 + sin(w0)^2+cos(w0)^2 == w1 + 1)
17*x + 1
sage: ((x-1)*(sin(x)^2 + cos(x)^2)^2)._subs_expr(sin(w0)^2+cos(w0)^2 == 1)
x - 1
_sympy_()

Returns a Sympy version of this object.

EXAMPLES:

sage: pi._sympy_()
pi
sage: type(_)
<class 'sympy.core.numbers.Pi'>
add_to_both_sides()

Returns a relation obtained by adding x to both sides of this relation.

EXAMPLES:

sage: var('x y z')
(x, y, z)
sage: eqn = x^2 + y^2 + z^2 <= 1
sage: eqn.add_to_both_sides(-z^2)
x^2 + y^2 <= -z^2 + 1
sage: eqn.add_to_both_sides(I)
x^2 + y^2 + z^2 + I <= (I + 1)
arccos()

Return the arc cosine of self.

EXAMPLES:

sage: x.arccos()
arccos(x)
sage: SR(1).arccos()
0
sage: SR(1/2).arccos()
1/3*pi
sage: SR(0.4).arccos()
arccos(0.400000000000000)

Use .n() to get a numerical approximation:

sage: SR(0.4).arccos().n()
1.15927948072741
sage: plot(lambda x: SR(x).arccos(), -1,1)

TESTS:

sage: SR(oo).arccos()
...
RuntimeError: arccos_eval(): arccos(infinity) encountered
sage: SR(-oo).arccos()
...
RuntimeError: arccos_eval(): arccos(infinity) encountered
sage: SR(unsigned_infinity).arccos()
Infinity
arccosh()

Return the inverse hyperbolic cosine of self.

EXAMPLES:

sage: x.arccosh()
arccosh(x)
sage: SR(0).arccosh()
1/2*I*pi
sage: SR(1/2).arccosh()
arccosh(1/2)
sage: SR(CDF(1/2)).arccosh()
arccosh(0.5)

Use .n() to get a numerical approximation:

sage: SR(CDF(1/2)).arccosh().n()
1.0471975512*I
sage: maxima('acosh(0.5)')
1.047197551196598*%i

TESTS:

sage: SR(oo).arccosh()
+Infinity
sage: SR(-oo).arccosh()
+Infinity
sage: SR(unsigned_infinity).arccosh()
+Infinity
arcsin()

Return the arcsin of x, i.e., the number y between -pi and pi such that sin(y) == x.

EXAMPLES:

sage: x.arcsin()
arcsin(x)
sage: SR(0.5).arcsin()
arcsin(0.500000000000000)

Use .n() to get a numerical approximation:

sage: SR(0.5).arcsin().n()
0.523598775598299

sage: SR(0.999).arcsin()
arcsin(0.999000000000000)
sage: SR(-0.999).arcsin()
-arcsin(0.999000000000000)
sage: SR(0.999).arcsin().n()
1.52607123962616

TESTS:

sage: SR(oo).arcsin()
...
RuntimeError: arcsin_eval(): arcsin(infinity) encountered
sage: SR(-oo).arcsin()
...
RuntimeError: arcsin_eval(): arcsin(infinity) encountered
sage: SR(unsigned_infinity).arcsin()
Infinity
arcsinh()

Return the inverse hyperbolic sine of self.

EXAMPLES:

sage: x.arcsinh()
arcsinh(x)
sage: SR(0).arcsinh()
0
sage: SR(1).arcsinh()
arcsinh(1)
sage: SR(1.0).arcsinh()
arcsinh(1.00000000000000)

Use .n() to get a numerical approximation:

sage: SR(1.0).arcsinh().n()
0.881373587019543
sage: maxima('asinh(1.0)')
0.881373587019543
Sage automatically applies certain identities::
sage: SR(3/2).arcsinh().cosh() 1/2*sqrt(13)

TESTS:

sage: SR(oo).arcsinh()
+Infinity
sage: SR(-oo).arcsinh()
-Infinity
sage: SR(unsigned_infinity).arcsinh()
Infinity
arctan()

Return the arc tangent of self.

EXAMPLES:

sage: x = var('x')
sage: x.arctan()
arctan(x)
sage: SR(1).arctan()
1/4*pi
sage: SR(1/2).arctan()
arctan(1/2)
sage: SR(0.5).arctan()
arctan(0.500000000000000)

Use .n() to get a numerical approximation:

sage: SR(0.5).arctan().n()
0.463647609000806
sage: plot(lambda x: SR(x).arctan(), -20,20)

TESTS:

sage: SR(oo).arctan()
1/2*pi
sage: SR(-oo).arctan()
-1/2*pi
sage: SR(unsigned_infinity).arctan()
...
RuntimeError: arctan_eval(): arctan(unsigned_infinity) encountered
arctan2()

Return the inverse of the 2-variable tan function on self and x.

EXAMPLES:

sage: var('x,y')
(x, y)
sage: x.arctan2(y)
arctan2(x, y)
sage: SR(1/2).arctan2(1/2)
1/4*pi
sage: maxima.eval('atan2(1/2,1/2)')
'%pi/4'

sage: SR(-0.7).arctan2(SR(-0.6))
-pi + arctan(1.16666666666667)

Use .n() to get a numerical approximation:

sage: SR(-0.7).arctan2(SR(-0.6)).n()
-2.27942259892257

TESTS:

We compare a bunch of different evaluation points between Sage and Maxima:

sage: float(SR(0.7).arctan2(0.6))
0.8621700546672264
sage: maxima('atan2(0.7,0.6)')
.862170054667226...
sage: float(SR(0.7).arctan2(-0.6))
2.2794225989225669
sage: maxima('atan2(0.7,-0.6)')
2.279422598922567
sage: float(SR(-0.7).arctan2(0.6))
-0.8621700546672264
sage: maxima('atan2(-0.7,0.6)')
-.862170054667226...
sage: float(SR(-0.7).arctan2(-0.6))
-2.2794225989225669
sage: maxima('atan2(-0.7,-0.6)')
-2.279422598922567
sage: float(SR(0).arctan2(-0.6))
3.1415926535897931
sage: maxima('atan2(0,-0.6)')
3.141592653589793
sage: float(SR(0).arctan2(0.6))
0.0
sage: maxima('atan2(0,0.6)')
0.0
sage: SR(0).arctan2(0)
0

sage: SR(I).arctan2(1)
arctan2(I, 1)
sage: SR(CDF(0,1)).arctan2(1)
arctan2(1.0*I, 1)
sage: SR(1).arctan2(CDF(0,1))
arctan2(1, 1.0*I)

sage: SR(oo).arctan2(oo)
...
RuntimeError: arctan2_eval(): arctan2(infinity, infinity) encountered
sage: SR(oo).arctan2(0)
0
sage: SR(-oo).arctan2(0)
pi
sage: SR(-oo).arctan2(-2)
-pi
sage: SR(unsigned_infinity).arctan2(2)
...
RuntimeError: arctan2_eval(): arctan2(unsigned_infinity, x) encountered
sage: SR(2).arctan2(oo)
1/2*pi
sage: SR(2).arctan2(-oo)
-1/2*pi
sage: SR(2).arctan2(SR(unsigned_infinity))
...
RuntimeError: arctan2_eval(): arctan2(x, unsigned_infinity) encountered
arctanh()

Return the inverse hyperbolic tangent of self.

EXAMPLES:

sage: x.arctanh()
arctanh(x)
sage: SR(0).arctanh()
0
sage: SR(1/2).arctanh()
arctanh(1/2)
sage: SR(0.5).arctanh()
arctanh(0.500000000000000)

Use .n() to get a numerical approximation:

sage: SR(0.5).arctanh().n()
0.549306144334055
sage: SR(0.5).arctanh().tanh()
0.500000000000000
sage: maxima('atanh(0.5)')
.5493061443340...

TESTS:

sage: SR(1).arctanh()
+Infinity
sage: SR(-1).arctanh()
-Infinity

sage: SR(oo).arctanh()
-1/2*I*pi
sage: SR(-oo).arctanh()
1/2*I*pi
sage: SR(unsigned_infinity).arctanh()
...
RuntimeError: arctanh_eval(): arctanh(unsigned_infinity) encountered
args()

EXAMPLES:

sage: x,y = var('x,y')
sage: f = x + y
sage: f.arguments()
(x, y)

sage: g = f.function(x)
sage: g.arguments()
(x,)
arguments()

EXAMPLES:

sage: x,y = var('x,y')
sage: f = x + y
sage: f.arguments()
(x, y)

sage: g = f.function(x)
sage: g.arguments()
(x,)
assume()

Assume that this equation holds. This is relevant for symbolic integration, among other things.

EXAMPLES: We call the assume method to assume that x>2:

sage: (x > 2).assume()

Bool returns True below if the inequality is definitely known to be True.

sage: bool(x > 0)
True
sage: bool(x < 0)
False

This may or may not be True, so bool returns False:

sage: bool(x > 3)
False

TESTS:

sage: v,c = var('v,c')
sage: assume(c != 0)
sage: integral((1+v^2/c^2)^3/(1-v^2/c^2)^(3/2),v)
-75/8*sqrt(c^2)*arcsin(sqrt(c^2)*v/c^2) - 17/8*v^3/(sqrt(-v^2/c^2 + 1)*c^2) - 1/4*v^5/(sqrt(-v^2/c^2 + 1)*c^4) + 83/8*v/sqrt(-v^2/c^2 + 1)
binomial()

Return binomial coefficient “self choose k”.

OUTPUT:
symbolic expression
EXAMPLES:
sage: var(‘x, y’) (x, y) sage: SR(5).binomial(SR(3)) 10 sage: x.binomial(SR(3)) 1/6*x^3 - 1/2*x^2 + 1/3*x sage: x.binomial(y) binomial(x,y)
coeff()

Returns the coefficient of s^n in this symbolic expression.

INPUT:

  • s - expression
  • n - integer, default 1

OUTPUT:

  • coefficient of s^n

Sometimes it may be necessary to expand or factor first, since this is not done automatically.

EXAMPLES:

sage: var('x,y,a')
(x, y, a)
sage: f = 100 + a*x + x^3*sin(x*y) + x*y + x/y + 2*sin(x*y)/x; f
x^3*sin(x*y) + a*x + x*y + x/y + 2*sin(x*y)/x + 100
sage: f.collect(x)
x^3*sin(x*y) + (a + y + 1/y)*x + 2*sin(x*y)/x + 100
sage: f.coefficient(x,0)
100
sage: f.coefficient(x,-1)
2*sin(x*y)
sage: f.coefficient(x,1)
a + y + 1/y
sage: f.coefficient(x,2)
0
sage: f.coefficient(x,3)
sin(x*y)
sage: f.coefficient(x^3)
sin(x*y)
sage: f.coefficient(sin(x*y))
x^3 + 2/x
sage: f.collect(sin(x*y))
(x^3 + 2/x)*sin(x*y) + a*x + x*y + x/y + 100

sage: var('a, x, y, z')
(a, x, y, z)
sage: f = (a*sqrt(2))*x^2 + sin(y)*x^(1/2) + z^z   
sage: f.coefficient(sin(y))
sqrt(x)        
sage: f.coefficient(x^2)
sqrt(2)*a
sage: f.coefficient(x^(1/2))
sin(y)
sage: f.coefficient(1)
0
sage: f.coefficient(x, 0)
sqrt(x)*sin(y) + z^z
coefficient()

Returns the coefficient of s^n in this symbolic expression.

INPUT:

  • s - expression
  • n - integer, default 1

OUTPUT:

  • coefficient of s^n

Sometimes it may be necessary to expand or factor first, since this is not done automatically.

EXAMPLES:

sage: var('x,y,a')
(x, y, a)
sage: f = 100 + a*x + x^3*sin(x*y) + x*y + x/y + 2*sin(x*y)/x; f
x^3*sin(x*y) + a*x + x*y + x/y + 2*sin(x*y)/x + 100
sage: f.collect(x)
x^3*sin(x*y) + (a + y + 1/y)*x + 2*sin(x*y)/x + 100
sage: f.coefficient(x,0)
100
sage: f.coefficient(x,-1)
2*sin(x*y)
sage: f.coefficient(x,1)
a + y + 1/y
sage: f.coefficient(x,2)
0
sage: f.coefficient(x,3)
sin(x*y)
sage: f.coefficient(x^3)
sin(x*y)
sage: f.coefficient(sin(x*y))
x^3 + 2/x
sage: f.collect(sin(x*y))
(x^3 + 2/x)*sin(x*y) + a*x + x*y + x/y + 100

sage: var('a, x, y, z')
(a, x, y, z)
sage: f = (a*sqrt(2))*x^2 + sin(y)*x^(1/2) + z^z   
sage: f.coefficient(sin(y))
sqrt(x)        
sage: f.coefficient(x^2)
sqrt(2)*a
sage: f.coefficient(x^(1/2))
sin(y)
sage: f.coefficient(1)
0
sage: f.coefficient(x, 0)
sqrt(x)*sin(y) + z^z
coefficients()

Coefficients of this symbolic expression as a polynomial in x.

INPUT:

  • x - optional variable

OUTPUT:

  • A list of pairs (expr, n), where expr is a symbolic expression and n is a power.

EXAMPLES:

sage: var('x, y, a')
(x, y, a)
sage: p = x^3 - (x-3)*(x^2+x) + 1
sage: p.coefficients()
[[1, 0], [3, 1], [2, 2]]
sage: p = expand((x-a*sqrt(2))^2 + x + 1); p
-2*sqrt(2)*a*x + 2*a^2 + x^2 + x + 1
sage: p.coefficients(a)
[[x^2 + x + 1, 0], [-2*sqrt(2)*x, 1], [2, 2]]
sage: p.coefficients(x)
[[2*a^2 + 1, 0], [-2*sqrt(2)*a + 1, 1], [1, 2]]

A polynomial with wacky exponents:

sage: p = (17/3*a)*x^(3/2) + x*y + 1/x + x^x
sage: p.coefficients(x)
[[1, -1], [x^x, 0], [y, 1], [17/3*a, 3/2]]
coeffs()

Coefficients of this symbolic expression as a polynomial in x.

INPUT:

  • x - optional variable

OUTPUT:

  • A list of pairs (expr, n), where expr is a symbolic expression and n is a power.

EXAMPLES:

sage: var('x, y, a')
(x, y, a)
sage: p = x^3 - (x-3)*(x^2+x) + 1
sage: p.coefficients()
[[1, 0], [3, 1], [2, 2]]
sage: p = expand((x-a*sqrt(2))^2 + x + 1); p
-2*sqrt(2)*a*x + 2*a^2 + x^2 + x + 1
sage: p.coefficients(a)
[[x^2 + x + 1, 0], [-2*sqrt(2)*x, 1], [2, 2]]
sage: p.coefficients(x)
[[2*a^2 + 1, 0], [-2*sqrt(2)*a + 1, 1], [1, 2]]

A polynomial with wacky exponents:

sage: p = (17/3*a)*x^(3/2) + x*y + 1/x + x^x
sage: p.coefficients(x)
[[1, -1], [x^x, 0], [y, 1], [17/3*a, 3/2]]
collect()

INPUT:

  • s - a symbol

OUTPUT:

  • expression

EXAMPLES:

sage: var('x,y,z')
(x, y, z)
sage: f = 4*x*y + x*z + 20*y^2 + 21*y*z + 4*z^2 + x^2*y^2*z^2
sage: f.collect(x)
x^2*y^2*z^2 + (4*y + z)*x + 20*y^2 + 21*y*z + 4*z^2
sage: f.collect(y)
(x^2*z^2 + 20)*y^2 + (4*x + 21*z)*y + x*z + 4*z^2
sage: f.collect(z)
(x^2*y^2 + 4)*z^2 + (x + 21*y)*z + 4*x*y + 20*y^2
collect_common_factors()

EXAMPLES:

sage: var('x')
x
sage: (x/(x^2 + x)).collect_common_factors()
1/(x + 1)
combine()

Returns a simplified version of this symbolic expression by combining all terms with the same denominator into a single term.

EXAMPLES:

sage: var('x, y, a, b, c')
(x, y, a, b, c)
sage: f = x*(x-1)/(x^2 - 7) + y^2/(x^2-7) + 1/(x+1) + b/a + c/a; f
(x - 1)*x/(x^2 - 7) + y^2/(x^2 - 7) + b/a + c/a + 1/(x + 1)
sage: f.combine()
((x - 1)*x + y^2)/(x^2 - 7) + (b + c)/a + 1/(x + 1)
conjugate()

Return the complex conjugate of this symbolic expression.

EXAMPLES:

sage: a = 1 + 2*I 
sage: a.conjugate()
-2*I + 1
sage: a = sqrt(2) + 3^(1/3)*I; a
sqrt(2) + I*3^(1/3)
sage: a.conjugate()
sqrt(2) - I*3^(1/3)

sage: SR(CDF.0).conjugate()
-1.0*I
sage: x.conjugate()
conjugate(x)
sage: SR(RDF(1.5)).conjugate()
1.5
sage: SR(float(1.5)).conjugate()
1.50000000000000
sage: SR(I).conjugate()
-I
sage: ( 1+I  + (2-3*I)*x).conjugate()
(3*I + 2)*conjugate(x) - I + 1
cos()

Return the cosine of self.

EXAMPLES:

sage: var('x, y')
(x, y)
sage: cos(x^2 + y^2)
cos(x^2 + y^2)
sage: cos(sage.symbolic.constants.pi)
-1
sage: cos(SR(1))
cos(1)
sage: cos(SR(RealField(150)(1)))
0.54030230586813971740093660744297660373231042

In order to get a numeric approximation use .n():

sage: SR(RR(1)).cos().n()
0.540302305868140
sage: SR(float(1)).cos().n()
0.540302305868140            

TESTS:

sage: SR(oo).cos()
...
RuntimeError: cos_eval(): cos(infinity) encountered
sage: SR(-oo).cos()
...
RuntimeError: cos_eval(): cos(infinity) encountered
sage: SR(unsigned_infinity).cos()
...
RuntimeError: cos_eval(): cos(infinity) encountered
cosh()

Return cosh of self.

We have $sinh(x) = (e^{x} + e^{-x})/2$.

EXAMPLES:

sage: x.cosh()
cosh(x)
sage: SR(1).cosh()
cosh(1)
sage: SR(0).cosh()
1
sage: SR(1.0).cosh()
cosh(1.00000000000000)

Use .n() to get a numerical approximation:

sage: SR(1.0).cosh().n()
1.54308063481524
sage: maxima('cosh(1.0)')
1.543080634815244
sage: SR(1.0000000000000000000000000).cosh()
cosh(1.000000000000000000000000)
sage: SR(1).cosh().n(90)
1.5430806348152437784779056
sage: SR(RIF(1)).cosh()
cosh(1)
sage: SR(RIF(1)).cosh().n()
1.543080634815244?

TESTS:

sage: SR(oo).cosh()
+Infinity
sage: SR(-oo).cosh()
+Infinity
sage: SR(unsigned_infinity).cosh()
...
RuntimeError: cosh_eval(): cosh(unsigned_infinity) encountered
csgn()

Return the sign of self, which is -1 if self < 0, 0 if self == 0, and 1 if self > 0, or unevaluated when self is a nonconstant symbolic expression.

It can be somewhat arbitrary when self is not real.

EXAMPLES:
sage: x = var(‘x’) sage: SR(-2).csgn() -1 sage: SR(0.0).csgn() 0 sage: SR(10).csgn() 1 sage: x.csgn() csgn(x) sage: SR(CDF.0).csgn() 1 sage: SR(I).csgn() 1
default_variable()

Return the default variable, which is by definition the first variable in self, or x is there are no variables in self. The result is cached.

EXAMPLES:

sage: sqrt(2).default_variable()
x        
sage: x, theta, a = var('x, theta, a')
sage: f = x^2 + theta^3 - a^x
sage: f.default_variable()
a

Note that this is the first variable, not the first argument:

sage: f(theta, a, x) = a + theta^3
sage: f.default_variable()
a
sage: f.variables()
(a, theta)
sage: f.arguments()
(theta, a, x)
degree()

Return the exponent of the highest nonnegative power of s in self.

OUTPUT:

  • an integer >= 0.

EXAMPLES:

sage: var('x,y,a')
(x, y, a)
sage: f = 100 + a*x + x^3*sin(x*y) + x*y + x/y^10 + 2*sin(x*y)/x; f
x^3*sin(x*y) + a*x + x*y + 2*sin(x*y)/x + x/y^10 + 100
sage: f.degree(x)
3
sage: f.degree(y)
1
sage: f.degree(sin(x*y))
1
sage: (x^-3+y).degree(x)
0
denominator()

Returns the denominator of this symbolic expression. If the expression is not a quotient, then this will just return 1.

EXAMPLES:

sage: x, y, z, theta = var('x, y, z, theta')
sage: f = (sqrt(x) + sqrt(y) + sqrt(z))/(x^10 - y^10 - sqrt(theta))
sage: f.denominator()
sqrt(theta) - x^10 + y^10

sage: y = var('y')
sage: g = x + y/(x + 2); g
x + y/(x + 2)
sage: g.numerator()
x + y/(x + 2)
sage: g.denominator()
1
derivative()

Returns the derivative of this expressions with respect to the variables supplied in args.

Multiple variables and iteration counts may be supplied; see documentation for the global derivative() function for more details.

See also

_derivative()

EXAMPLES:

sage: var("x y")
(x, y)
sage: t = (x^2+y)^2
sage: t.derivative(x)
4*(x^2 + y)*x
sage: t.derivative(x, 2)
12*x^2 + 4*y
sage: t.derivative(x, 2, y)
4
sage: t.derivative(y)
2*x^2 + 2*y
sage: t = sin(x+y^2)*tan(x*y)
sage: t.derivative(x)
(tan(x*y)^2 + 1)*y*sin(y^2 + x) + cos(y^2 + x)*tan(x*y)
sage: t.derivative(y)
(tan(x*y)^2 + 1)*x*sin(y^2 + x) + 2*y*cos(y^2 + x)*tan(x*y)
sage: h = sin(x)/cos(x)
sage: derivative(h,x,x,x)
6*sin(x)^4/cos(x)^4 + 8*sin(x)^2/cos(x)^2 + 2
sage: derivative(h,x,3)
6*sin(x)^4/cos(x)^4 + 8*sin(x)^2/cos(x)^2 + 2
sage: var('x, y')
(x, y)
sage: u = (sin(x) + cos(y))*(cos(x) - sin(y))
sage: derivative(u,x,y)
sin(x)*sin(y) - cos(x)*cos(y)            
sage: f = ((x^2+1)/(x^2-1))^(1/4)
sage: g = derivative(f, x); g # this is a complex expression
1/2*(x/(x^2 - 1) - (x^2 + 1)*x/(x^2 - 1)^2)/((x^2 + 1)/(x^2 - 1))^(3/4)
sage: g.factor()
-x/((x^2 - 1)^(5/4)*(x^2 + 1)^(3/4))
sage: y = var('y')
sage: f = y^(sin(x))
sage: derivative(f, x)
y^sin(x)*log(y)*cos(x)
sage: g(x) = sqrt(5-2*x)
sage: g_3 = derivative(g, x, 3); g_3(2)
-3
sage: f = x*e^(-x)
sage: derivative(f, 100)
x*e^(-x) - 100*e^(-x)
sage: g = 1/(sqrt((x^2-1)*(x+5)^6))
sage: derivative(g, x)
-((x + 5)^6*x + 3*(x + 5)^5*(x^2 - 1))/((x + 5)^6*(x^2 - 1))^(3/2)

TESTS:

sage: t.derivative()
...
ValueError: No differentiation variable specified.
diff()

Returns the derivative of this expressions with respect to the variables supplied in args.

Multiple variables and iteration counts may be supplied; see documentation for the global derivative() function for more details.

See also

_derivative()

EXAMPLES:

sage: var("x y")
(x, y)
sage: t = (x^2+y)^2
sage: t.derivative(x)
4*(x^2 + y)*x
sage: t.derivative(x, 2)
12*x^2 + 4*y
sage: t.derivative(x, 2, y)
4
sage: t.derivative(y)
2*x^2 + 2*y
sage: t = sin(x+y^2)*tan(x*y)
sage: t.derivative(x)
(tan(x*y)^2 + 1)*y*sin(y^2 + x) + cos(y^2 + x)*tan(x*y)
sage: t.derivative(y)
(tan(x*y)^2 + 1)*x*sin(y^2 + x) + 2*y*cos(y^2 + x)*tan(x*y)
sage: h = sin(x)/cos(x)
sage: derivative(h,x,x,x)
6*sin(x)^4/cos(x)^4 + 8*sin(x)^2/cos(x)^2 + 2
sage: derivative(h,x,3)
6*sin(x)^4/cos(x)^4 + 8*sin(x)^2/cos(x)^2 + 2
sage: var('x, y')
(x, y)
sage: u = (sin(x) + cos(y))*(cos(x) - sin(y))
sage: derivative(u,x,y)
sin(x)*sin(y) - cos(x)*cos(y)            
sage: f = ((x^2+1)/(x^2-1))^(1/4)
sage: g = derivative(f, x); g # this is a complex expression
1/2*(x/(x^2 - 1) - (x^2 + 1)*x/(x^2 - 1)^2)/((x^2 + 1)/(x^2 - 1))^(3/4)
sage: g.factor()
-x/((x^2 - 1)^(5/4)*(x^2 + 1)^(3/4))
sage: y = var('y')
sage: f = y^(sin(x))
sage: derivative(f, x)
y^sin(x)*log(y)*cos(x)
sage: g(x) = sqrt(5-2*x)
sage: g_3 = derivative(g, x, 3); g_3(2)
-3
sage: f = x*e^(-x)
sage: derivative(f, 100)
x*e^(-x) - 100*e^(-x)
sage: g = 1/(sqrt((x^2-1)*(x+5)^6))
sage: derivative(g, x)
-((x + 5)^6*x + 3*(x + 5)^5*(x^2 - 1))/((x + 5)^6*(x^2 - 1))^(3/2)

TESTS:

sage: t.derivative()
...
ValueError: No differentiation variable specified.
differentiate()

Returns the derivative of this expressions with respect to the variables supplied in args.

Multiple variables and iteration counts may be supplied; see documentation for the global derivative() function for more details.

See also

_derivative()

EXAMPLES:

sage: var("x y")
(x, y)
sage: t = (x^2+y)^2
sage: t.derivative(x)
4*(x^2 + y)*x
sage: t.derivative(x, 2)
12*x^2 + 4*y
sage: t.derivative(x, 2, y)
4
sage: t.derivative(y)
2*x^2 + 2*y
sage: t = sin(x+y^2)*tan(x*y)
sage: t.derivative(x)
(tan(x*y)^2 + 1)*y*sin(y^2 + x) + cos(y^2 + x)*tan(x*y)
sage: t.derivative(y)
(tan(x*y)^2 + 1)*x*sin(y^2 + x) + 2*y*cos(y^2 + x)*tan(x*y)
sage: h = sin(x)/cos(x)
sage: derivative(h,x,x,x)
6*sin(x)^4/cos(x)^4 + 8*sin(x)^2/cos(x)^2 + 2
sage: derivative(h,x,3)
6*sin(x)^4/cos(x)^4 + 8*sin(x)^2/cos(x)^2 + 2
sage: var('x, y')
(x, y)
sage: u = (sin(x) + cos(y))*(cos(x) - sin(y))
sage: derivative(u,x,y)
sin(x)*sin(y) - cos(x)*cos(y)            
sage: f = ((x^2+1)/(x^2-1))^(1/4)
sage: g = derivative(f, x); g # this is a complex expression
1/2*(x/(x^2 - 1) - (x^2 + 1)*x/(x^2 - 1)^2)/((x^2 + 1)/(x^2 - 1))^(3/4)
sage: g.factor()
-x/((x^2 - 1)^(5/4)*(x^2 + 1)^(3/4))
sage: y = var('y')
sage: f = y^(sin(x))
sage: derivative(f, x)
y^sin(x)*log(y)*cos(x)
sage: g(x) = sqrt(5-2*x)
sage: g_3 = derivative(g, x, 3); g_3(2)
-3
sage: f = x*e^(-x)
sage: derivative(f, 100)
x*e^(-x) - 100*e^(-x)
sage: g = 1/(sqrt((x^2-1)*(x+5)^6))
sage: derivative(g, x)
-((x + 5)^6*x + 3*(x + 5)^5*(x^2 - 1))/((x + 5)^6*(x^2 - 1))^(3/2)

TESTS:

sage: t.derivative()
...
ValueError: No differentiation variable specified.
divide_both_sides()

Returns a relation obtained by dividing both sides of this relation by x.

Note

The checksign keyword argument is currently ignored and is included for backward compatibility reasons only.

EXAMPLES:

sage: theta = var('theta')
sage: eqn =   (x^3 + theta < sin(x*theta))
sage: eqn.divide_both_sides(theta, checksign=False)
(x^3 + theta)/theta < sin(theta*x)/theta
sage: eqn.divide_both_sides(theta)
(x^3 + theta)/theta < sin(theta*x)/theta
sage: eqn/theta
(x^3 + theta)/theta < sin(theta*x)/theta        
exp()

Return exponential function of self, i.e., e to the power of self.

EXAMPLES:

sage: x.exp()
e^x
sage: SR(0).exp()
1
sage: SR(1/2).exp()
e^(1/2)
sage: SR(0.5).exp()
e^0.500000000000000
sage: (pi*I).exp()
-1

Use .n() to get a numerical approximation:

sage: SR(0.5).exp().n()
1.64872127070013
sage: math.exp(0.5)
1.6487212707001282

sage: SR(0.5).exp().log()
0.500000000000000

TESTS:

Test if #6377 is fixed:

sage: SR(oo).exp()
+Infinity
sage: SR(-oo).exp()
0
sage: SR(unsigned_infinity).exp()
...
RuntimeError: exp_eval(): exp^(unsigned_infinity) encountered
exp_simplify()

Simplifies this symbolic expression, which can contain logs, exponentials, and radicals, by converting it into a form which is canonical over a large class of expressions and a given ordering of variables

DETAILS: This uses the Maxima radcan() command. From the Maxima documentation: “All functionally equivalent forms are mapped into a unique form. For a somewhat larger class of expressions, produces a regular form. Two equivalent expressions in this class do not necessarily have the same appearance, but their difference can be simplified by radcan to zero. For some expressions radcan is quite time consuming. This is the cost of exploring certain relationships among the components of the expression for simplifications based on factoring and partial fraction expansions of exponents.”

ALIAS: radical_simplify, simplify_radical, simplify_log, log_simplify, exp_simplify, simplify_exp are all the same

EXAMPLES:

sage: var('x,y,a')
(x, y, a)
sage: f = log(x*y)
sage: f.simplify_radical()
log(x) + log(y)
sage: f = (log(x+x^2)-log(x))^a/log(1+x)^(a/2)
sage: f.simplify_radical()
log(x + 1)^(1/2*a)
sage: f = (e^x-1)/(1+e^(x/2))
sage: f.simplify_exp()
e^(1/2*x) - 1
expand()

Expand this symbolic expression. Products of sums and exponentiated sums are multiplied out, numerators of rational expressions which are sums are split into their respective terms, and multiplications are distributed over addition at all levels.

EXAMPLES:

We expand the expression (x-y)^5 using both method and functional notation.

sage: x,y = var('x,y')
sage: a = (x-y)^5
sage: a.expand()
x^5 - 5*x^4*y + 10*x^3*y^2 - 10*x^2*y^3 + 5*x*y^4 - y^5
sage: expand(a)
x^5 - 5*x^4*y + 10*x^3*y^2 - 10*x^2*y^3 + 5*x*y^4 - y^5

We expand some other expressions:

sage: expand((x-1)^3/(y-1))
x^3/(y - 1) - 3*x^2/(y - 1) + 3*x/(y - 1) - 1/(y - 1)
sage: expand((x+sin((x+y)^2))^2)
x^2 + 2*x*sin((x + y)^2) + sin((x + y)^2)^2

We can expand individual sides of a relation:

sage: a = (16*x-13)^2 == (3*x+5)^2/2
sage: a.expand()
256*x^2 - 416*x + 169 == 9/2*x^2 + 15*x + 25/2
sage: a.expand('left')
256*x^2 - 416*x + 169 == 1/2*(3*x + 5)^2
sage: a.expand('right')
(16*x - 13)^2 == 9/2*x^2 + 15*x + 25/2

TESTS:

sage: var(‘x,y’) (x, y) sage: ((x + (2/3)*y)^3).expand() x^3 + 2*x^2*y + 4/3*x*y^2 + 8/27*y^3 sage: expand( (x*sin(x) - cos(y)/x)^2 ) x^2*sin(x)^2 - 2*sin(x)*cos(y) + cos(y)^2/x^2 sage: f = (x-y)*(x+y); f (x - y)*(x + y) sage: f.expand() x^2 - y^2
expand_rational()

Expand this symbolic expression. Products of sums and exponentiated sums are multiplied out, numerators of rational expressions which are sums are split into their respective terms, and multiplications are distributed over addition at all levels.

EXAMPLES:

We expand the expression (x-y)^5 using both method and functional notation.

sage: x,y = var('x,y')
sage: a = (x-y)^5
sage: a.expand()
x^5 - 5*x^4*y + 10*x^3*y^2 - 10*x^2*y^3 + 5*x*y^4 - y^5
sage: expand(a)
x^5 - 5*x^4*y + 10*x^3*y^2 - 10*x^2*y^3 + 5*x*y^4 - y^5

We expand some other expressions:

sage: expand((x-1)^3/(y-1))
x^3/(y - 1) - 3*x^2/(y - 1) + 3*x/(y - 1) - 1/(y - 1)
sage: expand((x+sin((x+y)^2))^2)
x^2 + 2*x*sin((x + y)^2) + sin((x + y)^2)^2

We can expand individual sides of a relation:

sage: a = (16*x-13)^2 == (3*x+5)^2/2
sage: a.expand()
256*x^2 - 416*x + 169 == 9/2*x^2 + 15*x + 25/2
sage: a.expand('left')
256*x^2 - 416*x + 169 == 1/2*(3*x + 5)^2
sage: a.expand('right')
(16*x - 13)^2 == 9/2*x^2 + 15*x + 25/2

TESTS:

sage: var(‘x,y’) (x, y) sage: ((x + (2/3)*y)^3).expand() x^3 + 2*x^2*y + 4/3*x*y^2 + 8/27*y^3 sage: expand( (x*sin(x) - cos(y)/x)^2 ) x^2*sin(x)^2 - 2*sin(x)*cos(y) + cos(y)^2/x^2 sage: f = (x-y)*(x+y); f (x - y)*(x + y) sage: f.expand() x^2 - y^2
expand_trig()

Expands trigonometric and hyperbolic functions of sums of angles and of multiple angles occurring in self. For best results, self should already be expanded.

INPUT:

  • full - (default: False) To enhance user control of simplification, this function expands only one level at a time by default, expanding sums of angles or multiple angles. To obtain full expansion into sines and cosines immediately, set the optional parameter full to True.
  • half_angles - (default: False) If True, causes half-angles to be simplified away.
  • plus - (default: True) Controls the sum rule; expansion of sums (e.g. ‘sin(x + y)’) will take place only if plus is True.
  • times - (default: True) Controls the product rule, expansion of products (e.g. sin(2*x)) will take place only if times is True.

OUTPUT: a symbolic expression

EXAMPLES:

sage: sin(5*x).expand_trig()
sin(x)^5 - 10*sin(x)^3*cos(x)^2 + 5*sin(x)*cos(x)^4
sage: cos(2*x + var('y')).expand_trig()
-sin(2*x)*sin(y) + cos(2*x)*cos(y)

We illustrate various options to this function:

sage: f = sin(sin(3*cos(2*x))*x)
sage: f.expand_trig()
sin(-(sin(cos(2*x))^3 - 3*sin(cos(2*x))*cos(cos(2*x))^2)*x)
sage: f.expand_trig(full=True)
sin(((sin(sin(x)^2)*cos(cos(x)^2) - sin(cos(x)^2)*cos(sin(x)^2))^3 - 3*(sin(sin(x)^2)*cos(cos(x)^2) - sin(cos(x)^2)*cos(sin(x)^2))*(sin(sin(x)^2)*sin(cos(x)^2) + cos(sin(x)^2)*cos(cos(x)^2))^2)*x)
sage: sin(2*x).expand_trig(times=False)
sin(2*x)
sage: sin(2*x).expand_trig(times=True)
2*sin(x)*cos(x)
sage: sin(2 + x).expand_trig(plus=False)
sin(x + 2)
sage: sin(2 + x).expand_trig(plus=True)
sin(2)*cos(x) + sin(x)*cos(2)
sage: sin(x/2).expand_trig(half_angles=False)
sin(1/2*x)
sage: sin(x/2).expand_trig(half_angles=True)
1/2*sqrt(-cos(x) + 1)*sqrt(2)*(-1)^floor(1/2*x/pi)

ALIASES:

trig_expand() and expand_trig() are the same

factor()

Factors self, containing any number of variables or functions, into factors irreducible over the integers.

INPUT:

  • self - a symbolic expression
  • dontfactor - list (default: []), a list of variables with respect to which factoring is not to occur. Factoring also will not take place with respect to any variables which are less important (using the variable ordering assumed for CRE form) than those on the ‘dontfactor’ list.

EXAMPLES:

sage: x,y,z = var('x, y, z')
sage: (x^3-y^3).factor()
(x - y)*(x^2 + x*y + y^2)
sage: factor(-8*y - 4*x + z^2*(2*y + x))
(z - 2)*(z + 2)*(x + 2*y)
sage: f = -1 - 2*x - x^2 + y^2 + 2*x*y^2 + x^2*y^2
sage: F = factor(f/(36*(1 + 2*y + y^2)), dontfactor=[x]); F
1/36*(y - 1)*(x^2 + 2*x + 1)/(y + 1)

If you are factoring a polynomial with rational coefficients (and dontfactor is empty) the factorization is done using Singular instead of Maxima, so the following is very fast instead of dreadfully slow:

sage: var('x,y')
(x, y)
sage: (x^99 + y^99).factor()
(x + y)*(x^2 - x*y + y^2)*(x^6 - x^3*y^3 + y^6)*...
factor_list()

Returns a list of the factors of self, as computed by the factor command.

INPUT:

  • self - a symbolic expression
  • dontfactor - see docs for factor()

Note

If you already have a factored expression and just want to get at the individual factors, use _factor_list() instead.

EXAMPLES:

sage: var('x, y, z')
(x, y, z)
sage: f = x^3-y^3
sage: f.factor()
(x - y)*(x^2 + x*y + y^2)

Notice that the -1 factor is separated out:

sage: f.factor_list()
[(x - y, 1), (x^2 + x*y + y^2, 1)]

We factor a fairly straightforward expression:

sage: factor(-8*y - 4*x + z^2*(2*y + x)).factor_list()
[(z - 2, 1), (z + 2, 1), (x + 2*y, 1)]

A more complicated example:

sage: var('x, u, v')
(x, u, v)
sage: f = expand((2*u*v^2-v^2-4*u^3)^2 * (-u)^3 * (x-sin(x))^3) 
sage: f.factor()
-(x - sin(x))^3*(4*u^3 - 2*u*v^2 + v^2)^2*u^3
sage: g = f.factor_list(); g                     
[(x - sin(x), 3), (4*u^3 - 2*u*v^2 + v^2, 2), (u, 3), (-1, 1)]

This function also works for quotients:

sage: f = -1 - 2*x - x^2 + y^2 + 2*x*y^2 + x^2*y^2
sage: g = f/(36*(1 + 2*y + y^2)); g
1/36*(x^2*y^2 + 2*x*y^2 - x^2 + y^2 - 2*x - 1)/(y^2 + 2*y + 1)
sage: g.factor(dontfactor=[x])
1/36*(y - 1)*(x^2 + 2*x + 1)/(y + 1)
sage: g.factor_list(dontfactor=[x])
[(y - 1, 1), (y + 1, -1), (x^2 + 2*x + 1, 1), (1/36, 1)]

This example also illustrates that the exponents do not have to be integers:

sage: f = x^(2*sin(x)) * (x-1)^(sqrt(2)*x); f
(x - 1)^(sqrt(2)*x)*x^(2*sin(x))
sage: f.factor_list()
[(x - 1, sqrt(2)*x), (x, 2*sin(x))]
factorial()

Return the factorial of self.

OUTPUT:
symbolic expression
EXAMPLES:
sage: var(‘x, y’) (x, y) sage: SR(5).factorial() 120 sage: x.factorial() factorial(x) sage: (x^2+y^3).factorial() factorial(x^2 + y^3)
find()

Find all occurrences of the given pattern in this expression.

Note that once a subexpression matches the pattern, the search doesn’t extend to subexpressions of it.

EXAMPLES:

sage: var('x,y,z,a,b')
(x, y, z, a, b)
sage: w0 = SR.wild(0); w1 = SR.wild(1)

sage: (sin(x)*sin(y)).find(sin(w0))
[sin(x), sin(y)]

sage: ((sin(x)+sin(y))*(a+b)).expand().find(sin(w0))
[sin(x), sin(y)]

sage: (1+x+x^2+x^3).find(x)
[x]
sage: (1+x+x^2+x^3).find(x^w0)
[x^3, x^2]

sage: (1+x+x^2+x^3).find(y)
[]

# subexpressions of a match are not listed
sage: ((x^y)^z).find(w0^w1)
[(x^y)^z]
find_maximum_on_interval()

Numerically find the maximum of the expression self on the interval [a,b] (or [b,a]) along with the point at which the maximum is attained.

See the documentation for self.find_minimum_on_interval for more details.

EXAMPLES:

sage: f = x*cos(x)
sage: f.find_maximum_on_interval(0,5)
(0.5610963381910451, 0.8603335890...)
sage: f.find_maximum_on_interval(0,5, tol=0.1, maxfun=10)
(0.561090323458081..., 0.857926501456...)
find_minimum_on_interval()

Numerically find the minimum of the expression self on the interval [a,b] (or [b,a]) and the point at which it attains that minimum. Note that self must be a function of (at most) one variable.

INPUT:

  • var - variable (default: first variable in self)
  • a,b - endpoints of interval on which to minimize self.
  • tol - the convergence tolerance
  • maxfun - maximum function evaluations

OUTPUT:

  • minval - (float) the minimum value that self takes on in the interval [a,b]
  • x - (float) the point at which self takes on the minimum value

EXAMPLES:

sage: f = x*cos(x)
sage: f.find_minimum_on_interval(1, 5)
(-3.288371395590..., 3.4256184695...)
sage: f.find_minimum_on_interval(1, 5, tol=1e-3)
(-3.288371361890..., 3.4257507903...)
sage: f.find_minimum_on_interval(1, 5, tol=1e-2, maxfun=10)
(-3.288370845983..., 3.4250840220...)
sage: show(f.plot(0, 20))
sage: f.find_minimum_on_interval(1, 15)
(-9.477294259479..., 9.5293344109...)

ALGORITHM:

Uses scipy.optimize.fminbound which uses Brent’s method.

AUTHORS:

  • William Stein (2007-12-07)
find_root()

Numerically find a root of self on the closed interval [a,b] (or [b,a]) if possible, where self is a function in the one variable.

INPUT:

  • a, b - endpoints of the interval
  • var - optional variable
  • xtol, rtol - the routine converges when a root is known to lie within xtol of the value return. Should be = 0. The routine modifies this to take into account the relative precision of doubles.
  • maxiter - integer; if convergence is not achieved in maxiter iterations, an error is raised. Must be = 0.
  • full_output - bool (default: False), if True, also return object that contains information about convergence.

EXAMPLES:

Note that in this example both f(-2) and f(3) are positive, yet we still find a root in that interval:

sage: f = x^2 - 1
sage: f.find_root(-2, 3)
1.0
sage: f.find_root(-2, 3, x)
1.0
sage: z, result = f.find_root(-2, 3, full_output=True)
sage: result.converged
True
sage: result.flag
'converged'
sage: result.function_calls
11
sage: result.iterations
10
sage: result.root
1.0

More examples:

sage: (sin(x) + exp(x)).find_root(-10, 10)
-0.588532743981862...
sage: sin(x).find_root(-1,1)
0.0
sage: (1/tan(x)).find_root(3,3.5)
3.1415926535...

An example with a square root:

sage: f = 1 + x + sqrt(x+2); f.find_root(-2,10)
-1.6180339887498949

Some examples that Ted Kosan came up with:

sage: t = var('t')
sage: v = 0.004*(9600*e^(-(1200*t)) - 2400*e^(-(300*t)))
sage: v.find_root(0, 0.002)
0.001540327067911417...
sage: a = .004*(8*e^(-(300*t)) - 8*e^(-(1200*t)))*(720000*e^(-(300*t)) - 11520000*e^(-(1200*t))) +.004*(9600*e^(-(1200*t)) - 2400*e^(-(300*t)))^2

There is a 0 very close to the origin:

sage: show(plot(a, 0, .002), xmin=0, xmax=.002)

Using solve does not work to find it:

sage: a.solve(t)
[]

However find_root works beautifully:

sage: a.find_root(0,0.002)
0.0004110514049349...

We illustrate that root finding is only implemented in one dimension:

sage: x, y = var('x,y')
sage: (x-y).find_root(-2,2)
...
NotImplementedError: root finding currently only implemented in 1 dimension.

TESTS:

Test the special case that failed for the first attempt to fix #3980:

sage: t = var('t')
sage: find_root(1/t - x,0,2)
...
NotImplementedError: root finding currently only implemented in 1 dimension.
forget()

Forget the given constraint.

EXAMPLES:

sage: var('x,y')
(x, y)
sage: forget()
sage: assume(x>0, y < 2)
sage: assumptions()
[x > 0, y < 2]
sage: forget(y < 2)
sage: assumptions()
[x > 0]
full_simplify()

Applies simplify_trig, simplify_rational, and simplify_radical to self (in that order).

ALIAS: simplify_full and full_simplify are the same.

EXAMPLES:

sage: a = log(8)/log(2)
sage: a.simplify_full()
3
sage: f = sin(x)^2 + cos(x)^2
sage: f.simplify_full()
1
sage: f = sin(x/(x^2 + x))
sage: f.simplify_full()
sin(1/(x + 1))
function()

Return a callable symbolic expression with the given variables.

EXAMPLES:

We will use several symbolic variables in the examples below:

sage: var('x, y, z, t, a, w, n')
(x, y, z, t, a, w, n)
sage: u = sin(x) + x*cos(y)
sage: g = u.function(x,y)
sage: g(x,y)
x*cos(y) + sin(x)
sage: g(t,z)
t*cos(z) + sin(t)
sage: g(x^2, x^y)
x^2*cos(x^y) + sin(x^2)
sage: f = (x^2 + sin(a*w)).function(a,x,w); f
(a, x, w) |--> x^2 + sin(a*w)
sage: f(1,2,3)
sin(3) + 4

Using the function() method we can obtain the above function f, but viewed as a function of different variables:

sage: h = f.function(w,a); h
(w, a) |--> x^2 + sin(a*w)

This notation also works:

sage: h(w,a) = f
sage: h
(w, a) |--> x^2 + sin(a*w)

You can even make a symbolic expression f into a function by writing f(x,y) = f:

sage: f = x^n + y^n; f
x^n + y^n
sage: f(x,y) = f
sage: f
(x, y) |--> x^n + y^n
sage: f(2,3)
2^n + 3^n
gamma()

Return the Gamma function evaluated at self.

EXAMPLES:
sage: x = var(‘x’) sage: x.gamma() gamma(x) sage: SR(2).gamma() 1 sage: SR(10).gamma() 362880 sage: SR(10.0r).gamma() gamma(10.0000000000000)

Use .n() to get a numerical approximation:

sage: SR(10.0r).gamma().n()
362880.000000000
sage: SR(CDF(1,1)).gamma()
gamma(1.0 + 1.0*I)
sage: SR(CDF(1,1)).gamma().n()
0.498015668118 - 0.154949828302*I

sage: gp('gamma(1+I)') # 32-bit
0.4980156681183560427136911175 - 0.1549498283018106851249551305*I

sage: gp('gamma(1+I)') # 64-bit
0.49801566811835604271369111746219809195 - 0.15494982830181068512495513048388660520*I

sage: set_verbose(-1); plot(lambda x: SR(x).gamma(), -6,4).show(ymin=-3,ymax=3)
gcd()

Return the gcd of self and b, which must be integers or polynomials over the rational numbers.

TODO: I tried the massive gcd from http://trac.sagemath.org/sage_trac/ticket/694 on Ginac dies after about 10 seconds. Singular easily does that GCD now. Since Ginac only handles poly gcd over QQ, we should change ginac itself to use Singular.

EXAMPLES:

sage: var('x,y')
(x, y)
sage: SR(10).gcd(SR(15))
5
sage: (x^3 - 1).gcd(x-1)
x - 1
sage: (x^3 - 1).gcd(x^2+x+1)
x^2 + x + 1
sage: (x^3 - sage.symbolic.constants.pi).gcd(x-sage.symbolic.constants.pi)
...
RuntimeError: gcd: arguments must be polynomials over the rationals
sage: gcd(x^3 - y^3, x-y)
-x + y
sage: gcd(x^100-y^100, x^10-y^10)
-x^10 + y^10
sage: gcd(expand( (x^2+17*x+3/7*y)*(x^5 - 17*y + 2/3) ), expand((x^13+17*x+3/7*y)*(x^5 - 17*y + 2/3)) )
1/7*x^5 - 17/7*y + 2/21
gradient()

Compute the gradient of a symbolic function.

This function returns a vector whose components are the derivatives of the original function with respect to the arguments of the original function. Alternatively, you can specify the variables as a list.

EXAMPLES:

sage: x,y = var('x y')
sage: f = x^2+y^2
sage: f.gradient()
(2*x, 2*y)
sage: g(x,y) = x^2+y^2
sage: g.gradient()
((x, y) |--> 2*x, (x, y) |--> 2*y)
sage: n = var('n')
sage: f(x,y) = x^n+y^n
sage: f.gradient()
((x, y) |--> n*x^(n - 1), (x, y) |--> n*y^(n - 1))
sage: f.gradient([y,x])
((x, y) |--> n*y^(n - 1), (x, y) |--> n*x^(n - 1))
has()

EXAMPLES:

sage: var('x,y,a'); w0 = SR.wild(); w1 = SR.wild()
(x, y, a)
sage: (x*sin(x + y + 2*a)).has(y)
True

Here “x+y” is not a subexpression of “x+y+2*a” (which has the subexpressions “x”, “y” and “2*a”):

sage: (x*sin(x + y + 2*a)).has(x+y)
False
sage: (x*sin(x + y + 2*a)).has(x + y + w0)
True

The following fails because “2*(x+y)” automatically gets converted to “2*x+2*y” of which “x+y” is not a subexpression:

sage: (x*sin(2*(x+y) + 2*a)).has(x+y)
False

Although x^1==x and x^0==1, neither “x” nor “1” are actually of the form “x^something”:

sage: (x+1).has(x^w0)
False

Here is another possible pitfall, where the first expression matches because the term “-x” has the form “(-1)*x” in GiNaC. To check whether a polynomial contains a linear term you should use the coeff() function instead.

sage: (4*x^2 - x + 3).has(w0*x)
True
sage: (4*x^2 + x + 3).has(w0*x)
False
sage: (4*x^2 + x + 3).has(x)
True
sage: (4*x^2 - x + 3).coeff(x,1)
-1
sage: (4*x^2 + x + 3).coeff(x,1)
1
hessian()

Compute the hessian of a function. This returns a matrix components are the 2nd partial derivatives of the original function.

EXAMPLES:

sage: x,y = var('x y')
sage: f = x^2+y^2
sage: f.hessian()
[2 0]
[0 2]
sage: g(x,y) = x^2+y^2
sage: g.hessian()
[(x, y) |--> 2 (x, y) |--> 0]
[(x, y) |--> 0 (x, y) |--> 2]
imag()

Return the imaginary part of this symbolic expression.

EXAMPLES:

sage: sqrt(-2).imag_part()
sqrt(2)

We simplify \ln(\exp(z)) to z for -\pi<{\rm Im}(z)<=\pi:

sage: z = var('z')
sage: f = log(exp(z))
sage: assume(-pi < imag(z))
sage: assume(imag(z) <= pi)
sage: f
log(e^z)
sage: f.simplify()
z
sage: forget()

A more symbolic example:

sage: var('a, b')
(a, b)
sage: f = log(a + b*I)
sage: f.imag_part()
arctan2(real_part(b) + imag_part(a), real_part(a) - imag_part(b))

TESTS:

sage: x = var('x')
sage: x.imag_part()
imag_part(x)
sage: SR(2+3*I).imag_part()
3
sage: SR(CC(2,3)).imag_part()
3.00000000000000
sage: SR(CDF(2,3)).imag_part()
3.0
imag_part()

Return the imaginary part of this symbolic expression.

EXAMPLES:

sage: sqrt(-2).imag_part()
sqrt(2)

We simplify \ln(\exp(z)) to z for -\pi<{\rm Im}(z)<=\pi:

sage: z = var('z')
sage: f = log(exp(z))
sage: assume(-pi < imag(z))
sage: assume(imag(z) <= pi)
sage: f
log(e^z)
sage: f.simplify()
z
sage: forget()

A more symbolic example:

sage: var('a, b')
(a, b)
sage: f = log(a + b*I)
sage: f.imag_part()
arctan2(real_part(b) + imag_part(a), real_part(a) - imag_part(b))

TESTS:

sage: x = var('x')
sage: x.imag_part()
imag_part(x)
sage: SR(2+3*I).imag_part()
3
sage: SR(CC(2,3)).imag_part()
3.00000000000000
sage: SR(CDF(2,3)).imag_part()
3.0
integral()

Compute the integral of self. Please see sage.calculus.calculus.integral for more details.

EXAMPLES:

sage: sin(x).integral(x,0,3)
-cos(3) + 1
sage: sin(x).integral(x)
-cos(x)
integrate()

Compute the integral of self. Please see sage.calculus.calculus.integral for more details.

EXAMPLES:

sage: sin(x).integral(x,0,3)
-cos(3) + 1
sage: sin(x).integral(x)
-cos(x)
inverse_laplace()

Return inverse Laplace transform of self. See sage.calculus.calculus.inverse_laplace

EXAMPLES:

sage: var('w, m')
(w, m)
sage: f = (1/(w^2+10)).inverse_laplace(w, m); f
1/10*sqrt(10)*sin(sqrt(10)*m)
is_polynomial()

Return True if self is a polynomial in the given variable.

EXAMPLES:

sage: var('x,y,z')
(x, y, z)
sage: t = x^2 + y; t
x^2 + y
sage: t.is_polynomial(x)
True
sage: t.is_polynomial(y)
True
sage: t.is_polynomial(z)
True

sage: t = sin(x) + y; t
y + sin(x)
sage: t.is_polynomial(x)
False
sage: t.is_polynomial(y)
True
sage: t.is_polynomial(sin(x))
True
is_relational()

Return True if self is a relational expression.

EXAMPLES:

sage: x = var('x')
sage: eqn = (x-1)^2 == x^2 - 2*x + 3
sage: eqn.is_relational()
True
sage: sin(x).is_relational()
False
is_unit()

Return True if this expression is a unit of the symbolic ring.

EXAMPLES:

sage: SR(1).is_unit()
True
sage: SR(-1).is_unit()
True
sage: SR(0).is_unit()
False
iterator()

Return an iterator over the arguments of this expression.

EXAMPLES:

sage: x,y,z = var('x,y,z')
sage: list((x+y+z).iterator())
[x, y, z]
sage: list((x*y*z).iterator())
[x, y, z]
sage: list((x^y*z*(x+y)).iterator())
[x + y, x^y, z]
laplace()

Return Laplace transform of self. See sage.calculus.calculus.laplace

EXAMPLES:

sage: var('x,s,z')
(x, s, z)
sage: (z + exp(x)).laplace(x, s)
z/s + 1/(s - 1)
leading_coeff()

Return the leading coefficient of s in self.

EXAMPLES:

sage: var('x,y,a')
(x, y, a)
sage: f = 100 + a*x + x^3*sin(x*y) + x*y + x/y + 2*sin(x*y)/x; f
x^3*sin(x*y) + a*x + x*y + x/y + 2*sin(x*y)/x + 100
sage: f.leading_coefficient(x)
sin(x*y)
sage: f.leading_coefficient(y)
x
sage: f.leading_coefficient(sin(x*y))
x^3 + 2/x
leading_coefficient()

Return the leading coefficient of s in self.

EXAMPLES:

sage: var('x,y,a')
(x, y, a)
sage: f = 100 + a*x + x^3*sin(x*y) + x*y + x/y + 2*sin(x*y)/x; f
x^3*sin(x*y) + a*x + x*y + x/y + 2*sin(x*y)/x + 100
sage: f.leading_coefficient(x)
sin(x*y)
sage: f.leading_coefficient(y)
x
sage: f.leading_coefficient(sin(x*y))
x^3 + 2/x
left()

If self is a relational expression, return the left hand side of the relation. Otherwise, raise a ValueError.

EXAMPLES:

sage: x = var('x')
sage: eqn = (x-1)^2 == x^2 - 2*x + 3
sage: eqn.left_hand_side()
(x - 1)^2
sage: eqn.lhs()
(x - 1)^2
sage: eqn.left()
(x - 1)^2
left_hand_side()

If self is a relational expression, return the left hand side of the relation. Otherwise, raise a ValueError.

EXAMPLES:

sage: x = var('x')
sage: eqn = (x-1)^2 == x^2 - 2*x + 3
sage: eqn.left_hand_side()
(x - 1)^2
sage: eqn.lhs()
(x - 1)^2
sage: eqn.left()
(x - 1)^2
lgamma()

Return the log-gamma function evaluated at self. This is the logarithm of gamma of self, where gamma is a complex function such that gamma(n) equals factorial(n-1).

EXAMPLES:
sage: x = var(‘x’) sage: x.lgamma() lgamma(x) sage: SR(2).lgamma() 0 sage: SR(5).lgamma() log(24) sage: SR(5-1).factorial().log() log(24) sage: set_verbose(-1); plot(lambda x: SR(x).lgamma(), -7,8, plot_points=1000).show() sage: math.exp(0.5) 1.6487212707001282 sage: plot(lambda x: (SR(x).exp() - SR(-x).exp())/2 - SR(x).sinh(), -1, 1)
lhs()

If self is a relational expression, return the left hand side of the relation. Otherwise, raise a ValueError.

EXAMPLES:

sage: x = var('x')
sage: eqn = (x-1)^2 == x^2 - 2*x + 3
sage: eqn.left_hand_side()
(x - 1)^2
sage: eqn.lhs()
(x - 1)^2
sage: eqn.left()
(x - 1)^2
limit()

Return a symbolic limit. See sage.calculus.calculus.limit

EXAMPLES:

sage: (sin(x)/x).limit(x=0)
1
log()

Return the logarithm of self.

EXAMPLES:

sage: x, y = var('x, y')
sage: x.log()
log(x)
sage: (x^y + y^x).log()
log(x^y + y^x)
sage: SR(0).log()
-Infinity
sage: SR(1).log()
0
sage: SR(1/2).log()
log(1/2)
sage: SR(0.5).log()
log(0.500000000000000)

Use .n() to get a numerical approximation:

sage: SR(0.5).log().n()
-0.693147180559945
sage: SR(0.5).log().exp()
0.500000000000000
sage: math.log(0.5)
-0.69314718055994529
sage: plot(lambda x: SR(x).log(), 0.1,10)

TESTS:

sage: SR(oo).log()
+Infinity
sage: SR(-oo).log()
+Infinity
sage: SR(unsigned_infinity).log()
+Infinity
log_simplify()

Simplifies this symbolic expression, which can contain logs, exponentials, and radicals, by converting it into a form which is canonical over a large class of expressions and a given ordering of variables

DETAILS: This uses the Maxima radcan() command. From the Maxima documentation: “All functionally equivalent forms are mapped into a unique form. For a somewhat larger class of expressions, produces a regular form. Two equivalent expressions in this class do not necessarily have the same appearance, but their difference can be simplified by radcan to zero. For some expressions radcan is quite time consuming. This is the cost of exploring certain relationships among the components of the expression for simplifications based on factoring and partial fraction expansions of exponents.”

ALIAS: radical_simplify, simplify_radical, simplify_log, log_simplify, exp_simplify, simplify_exp are all the same

EXAMPLES:

sage: var('x,y,a')
(x, y, a)
sage: f = log(x*y)
sage: f.simplify_radical()
log(x) + log(y)
sage: f = (log(x+x^2)-log(x))^a/log(1+x)^(a/2)
sage: f.simplify_radical()
log(x + 1)^(1/2*a)
sage: f = (e^x-1)/(1+e^(x/2))
sage: f.simplify_exp()
e^(1/2*x) - 1
low_degree()

Return the exponent of the lowest nonpositive power of s in self.

OUTPUT:

  • an integer <= 0.

EXAMPLES:

sage: var('x,y,a')
(x, y, a)
sage: f = 100 + a*x + x^3*sin(x*y) + x*y + x/y^10 + 2*sin(x*y)/x; f
x^3*sin(x*y) + a*x + x*y + 2*sin(x*y)/x + x/y^10 + 100
sage: f.low_degree(x)
-1
sage: f.low_degree(y)
-10
sage: f.low_degree(sin(x*y))
0
sage: (x^3+y).low_degree(x)
0
match()

Check if self matches the given pattern.

INPUT:

  • pattern - a symbolic expression, possibly containing wildcards to match for

OUTPUT:

  • None - if there is no match
  • a dictionary mapping the wildcards to the matching values if a match was found. Note that the dictionary is empty if there were no wildcards in the given pattern.

See also http://www.ginac.de/tutorial/Pattern-matching-and-advanced-substitutions.html

EXAMPLES:

sage: var('x,y,z,a,b,c,d,e,f')
(x, y, z, a, b, c, d, e, f)
sage: w0 = SR.wild(0); w1 = SR.wild(1); w2 = SR.wild(2)
sage: ((x+y)^a).match((x+y)^a)  # no wildcards, so empty dict
{}
sage: print ((x+y)^a).match((x+y)^b)
None
sage: t = ((x+y)^a).match(w0^w1)
sage: t[w0], t[w1]
(x + y, a)
sage: print ((x+y)^a).match(w0^w0)
None
sage: ((x+y)^(x+y)).match(w0^w0)
{$0: x + y}
sage: t = ((a+b)*(a+c)).match((a+w0)*(a+w1))
sage: t[w0], t[w1]
(b, c)
sage: ((a+b)*(a+c)).match((w0+b)*(w0+c))
{$0: a}
sage: print ((a+b)*(a+c)).match((w0+w1)*(w0+w2))    # surprising?
None
sage: t = (a*(x+y)+a*z+b).match(a*w0+w1)
sage: t[w0], t[w1]
(x + y, a*z + b)
sage: print (a+b+c+d+e+f).match(c)
None
sage: (a+b+c+d+e+f).has(c)
True
sage: (a+b+c+d+e+f).match(c+w0)
{$0: a + b + d + e + f}
sage: (a+b+c+d+e+f).match(c+e+w0)
{$0: a + b + d + f}
sage: (a+b).match(a+b+w0)
{$0: 0}
sage: print (a*b^2).match(a^w0*b^w1)
None
sage: (a*b^2).match(a*b^w1)
{$1: 2}
sage: (x*x.arctan2(x^2)).match(w0*w0.arctan2(w0^2))
{$0: x}

Beware that behind-the-scenes simplification can lead to surprising results in matching:

sage: print (x+x).match(w0+w1)
None
sage: t = x+x; t
2*x
sage: t.operator()
<built-in function mul>

Since asking to match w0+w1 looks for an addition operator, there is no match.

minpoly()

Return the minimal polynomial of this symbolic expression.

EXAMPLES:

sage: golden_ratio.minpoly()
x^2 - x - 1
multiply_both_sides()

Returns a relation obtained by multiplying both sides of this relation by x.

Note

The checksign keyword argument is currently ignored and is included for backward compatibility reasons only.

EXAMPLES:

sage: var('x,y'); f = x + 3 < y - 2
(x, y)
sage: f.multiply_both_sides(7)
7*x + 21 < 7*y - 14
sage: f.multiply_both_sides(-1/2)
-1/2*x - 3/2 < -1/2*y + 1
sage: f*(-2/3)
-2/3*x - 2 < -2/3*y + 4/3
sage: f*(-pi)
-(x + 3)*pi < -(y - 2)*pi

Since the direction of the inequality never changes when doing arithmetic with equations, you can multiply or divide the equation by a quantity with unknown sign:

sage: f*(1+I)
(I + 1)*x + 3*I + 3 < (I + 1)*y - 2*I - 2
sage: f = sqrt(2) + x == y^3
sage: f.multiply_both_sides(I)
I*x + I*sqrt(2) == I*y^3
sage: f.multiply_both_sides(-1)
-x - sqrt(2) == -y^3

Note that the direction of the following inequalities is not reversed:

sage: (x^3 + 1 > 2*sqrt(3)) * (-1)
-x^3 - 1 > -2*sqrt(3)
sage: (x^3 + 1 >= 2*sqrt(3)) * (-1)
-x^3 - 1 >= -2*sqrt(3)
sage: (x^3 + 1 <= 2*sqrt(3)) * (-1)
-x^3 - 1 <= -2*sqrt(3)        
n()

Return a numerical approximation this symbolic expression as either a real or complex number with at least the requested number of bits or digits of precision.

EXAMPLES:

sage: sin(x).subs(x=5).n()
-0.958924274663138
sage: sin(x).subs(x=5).n(100)
-0.95892427466313846889315440616
sage: sin(x).subs(x=5).n(digits=50)
-0.95892427466313846889315440615599397335246154396460
sage: zeta(x).subs(x=2).numerical_approx(digits=50)
1.6449340668482264364724151666460251892189499012068

sage: cos(3).numerical_approx(200)
-0.98999249660044545727157279473126130239367909661558832881409
sage: numerical_approx(cos(3), digits=10)
-0.9899924966
sage: (i + 1).numerical_approx(32)
1.00000000 + 1.00000000*I
sage: (pi + e + sqrt(2)).numerical_approx(100)
7.2740880444219335226246195788

TESTS:

We test the evaluation of different infinities available in Pynac:

sage: t = x - oo; t
-Infinity
sage: t.n()
-infinity
sage: t = x + oo; t
+Infinity
sage: t.n()
+infinity
sage: t = x - unsigned_infinity; t
Infinity
sage: t.n()
+infinity
nintegral()

Compute the numerical integral of self. Please see sage.calculus.calculus.nintegral for more details.

EXAMPLES:

sage: sin(x).nintegral(x,0,3)
(1.989992496600..., 2.209335488557...e-14, 21, 0)
nintegrate()

Compute the numerical integral of self. Please see sage.calculus.calculus.nintegral for more details.

EXAMPLES:

sage: sin(x).nintegral(x,0,3)
(1.989992496600..., 2.209335488557...e-14, 21, 0)
nops()

Returns the number of arguments of this expression.

EXAMPLES:

sage: var('a,b,c,x,y')
(a, b, c, x, y)
sage: a.number_of_operands()
0
sage: (a^2 + b^2 + (x+y)^2).number_of_operands()
3
sage: (a^2).number_of_operands()
2
sage: (a*b^2*c).number_of_operands()
3
norm()

The complex norm of this symbolic expression, i.e., the expression times its complex conjugate.

EXAMPLES:

sage: a = 1 + 2*I 
sage: a.norm()
5
sage: a = sqrt(2) + 3^(1/3)*I; a
sqrt(2) + I*3^(1/3)
sage: a.norm()
3^(2/3) + 2
sage: CDF(a).norm()
4.08008382305
sage: CDF(a.norm())
4.08008382305
number_of_arguments()

EXAMPLES:

sage: x,y = var('x,y')
sage: f = x + y
sage: f.number_of_arguments()
2

sage: g = f.function(x)
sage: g.number_of_arguments()
1
sage: x,y,z = var('x,y,z')
sage: (x+y).number_of_arguments()
2
sage: (x+1).number_of_arguments()
1
sage: (sin(x)+1).number_of_arguments()
1
sage: (sin(z)+x+y).number_of_arguments()
3
sage: (sin(x+y)).number_of_arguments()
2
sage: ( 2^(8/9) - 2^(1/9) )(x-1)
...
ValueError: the number of arguments must be less than or equal to 0
number_of_operands()

Returns the number of arguments of this expression.

EXAMPLES:

sage: var('a,b,c,x,y')
(a, b, c, x, y)
sage: a.number_of_operands()
0
sage: (a^2 + b^2 + (x+y)^2).number_of_operands()
3
sage: (a^2).number_of_operands()
2
sage: (a*b^2*c).number_of_operands()
3
numerator()

Returns the numerator of this symbolic expression. If the expression is not a quotient, then this will return the expression itself.

EXAMPLES:

sage: a, x, y = var('a,x,y')
sage: f = x*(x-a)/((x^2 - y)*(x-a)); f
x/(x^2 - y)
sage: f.numerator()
x
sage: f.denominator()
x^2 - y

sage: y = var('y')
sage: g = x + y/(x + 2); g
x + y/(x + 2)
sage: g.numerator()
x + y/(x + 2)
sage: g.denominator()
1
numerical_approx()

Return a numerical approximation this symbolic expression as either a real or complex number with at least the requested number of bits or digits of precision.

EXAMPLES:

sage: sin(x).subs(x=5).n()
-0.958924274663138
sage: sin(x).subs(x=5).n(100)
-0.95892427466313846889315440616
sage: sin(x).subs(x=5).n(digits=50)
-0.95892427466313846889315440615599397335246154396460
sage: zeta(x).subs(x=2).numerical_approx(digits=50)
1.6449340668482264364724151666460251892189499012068

sage: cos(3).numerical_approx(200)
-0.98999249660044545727157279473126130239367909661558832881409
sage: numerical_approx(cos(3), digits=10)
-0.9899924966
sage: (i + 1).numerical_approx(32)
1.00000000 + 1.00000000*I
sage: (pi + e + sqrt(2)).numerical_approx(100)
7.2740880444219335226246195788

TESTS:

We test the evaluation of different infinities available in Pynac:

sage: t = x - oo; t
-Infinity
sage: t.n()
-infinity
sage: t = x + oo; t
+Infinity
sage: t.n()
+infinity
sage: t = x - unsigned_infinity; t
Infinity
sage: t.n()
+infinity
operands()

Returns a list containing the operands of this expression.

EXAMPLES:

sage: var('a,b,c,x,y')
(a, b, c, x, y)
sage: (a^2 + b^2 + (x+y)^2).operands()
[(x + y)^2, a^2, b^2]
sage: (a^2).operands()
[a, 2]
sage: (a*b^2*c).operands()
[a, b^2, c]
operator()

Returns the topmost operator in this expression.

EXAMPLES:

sage: x,y,z = var('x,y,z')
sage: (x+y).operator()
<built-in function add>
sage: (x^y).operator()
<built-in function pow>
sage: (x^y * z).operator()
<built-in function mul>
sage: (x < y).operator()
<built-in function lt>

sage: abs(x).operator()
abs
sage: r = gamma(x).operator(); type(r)
<class 'sage.functions.other.Function_gamma'>

sage: from sage.symbolic.function import function 
sage: psi = function('psi', 1)
sage: psi(x).operator()
psi

sage: r = psi(x).operator()
sage: r == psi
True

sage: f = function('f', 1, conjugate_func=lambda x: 2*x)
sage: nf = f(x).operator()
sage: nf(x).conjugate()
2*x

sage: f = function('f')
sage: a = f(x).diff(x); a
D[0](f)(x)
sage: a.operator()
D[0](f)
TESTS:
sage: (x <= y).operator() <built-in function le> sage: (x == y).operator() <built-in function eq> sage: (x != y).operator() <built-in function ne> sage: (x > y).operator() <built-in function gt> sage: (x >= y).operator() <built-in function ge>
partial_fraction()

Return the partial fraction expansion of self with respect to the given variable.

INPUT:

  • var - variable name or string (default: first variable)

OUTPUT: Symbolic expression

EXAMPLES:

sage: f = x^2/(x+1)^3
sage: f.partial_fraction()
1/(x + 1) - 2/(x + 1)^2 + 1/(x + 1)^3
sage: f.partial_fraction()
1/(x + 1) - 2/(x + 1)^2 + 1/(x + 1)^3

Notice that the first variable in the expression is used by default:

sage: y = var('y')
sage: f = y^2/(y+1)^3
sage: f.partial_fraction()
1/(y + 1) - 2/(y + 1)^2 + 1/(y + 1)^3

sage: f = y^2/(y+1)^3 + x/(x-1)^3
sage: f.partial_fraction()
y^2/(y^3 + 3*y^2 + 3*y + 1) + 1/(x - 1)^2 + 1/(x - 1)^3

You can explicitly specify which variable is used:

sage: f.partial_fraction(y)
x/(x^3 - 3*x^2 + 3*x - 1) + 1/(y + 1) - 2/(y + 1)^2 + 1/(y + 1)^3
plot()

Plot a symbolic expression. All arguments are passed onto the standard plot command.

EXAMPLES:

This displays a straight line:

sage: sin(2).plot((x,0,3))

This draws a red oscillatory curve:

sage: sin(x^2).plot((x,0,2*pi), rgbcolor=(1,0,0))

Another plot using the variable theta:

sage: var('theta')
theta
sage: (cos(theta) - erf(theta)).plot((theta,-2*pi,2*pi))

A very thick green plot with a frame:

sage: sin(x).plot((x,-4*pi, 4*pi), thickness=20, rgbcolor=(0,0.7,0)).show(frame=True)

You can embed 2d plots in 3d space as follows:

sage: plot(sin(x^2), (x,-pi, pi), thickness=2).plot3d(z = 1)

A more complicated family:

sage: G = sum([plot(sin(n*x), (x,-2*pi, 2*pi)).plot3d(z=n) for n in [0,0.1,..1]])
sage: G.show(frame_aspect_ratio=[1,1,1/2])

A plot involving the floor function:

sage: plot(1.0 - x * floor(1/x), (x,0.00001,1.0))

Sage used to allow symbolic functions with “no arguments”; this no longer works:

sage: plot(2*sin, -4, 4)
...
TypeError: unsupported operand parent(s) for '*': 'Integer Ring' and '<class 'sage.functions.trig.Function_sin'>'

You should evaluate the function first:

sage: plot(2*sin(x), -4, 4)

TESTS:

sage: f(x) = x*(1 - x)
sage: plot(f,0,1)
poly()

Express this symbolic expression as a polynomial in x. If this is not a polynomial in x, then some coefficients may be functions of x.

Warning

This is different from polynomial() which returns a Sage polynomial over a given base ring.

EXAMPLES:

sage: var('a, x')
(a, x)
sage: p = expand((x-a*sqrt(2))^2 + x + 1); p
-2*sqrt(2)*a*x + 2*a^2 + x^2 + x + 1
sage: p.poly(a)
-2*sqrt(2)*a*x + 2*a^2 + x^2 + x + 1
sage: bool(expand(p.poly(a)) == p)
True            
sage: p.poly(x)
-(2*sqrt(2)*a - 1)*x + 2*a^2 + x^2 + 1
polynomial()

Return this symbolic expression as an algebraic polynomial over the given base ring, if possible.

The point of this function is that it converts purely symbolic polynomials into optimised algebraic polynomials over a given base ring.

Warning

This is different from meth:poly which is used to rewrite self as a polynomial in terms of one of the variables.

INPUT:

  • base_ring - a ring

EXAMPLES:

sage: f = x^2 -2/3*x + 1
sage: f.polynomial(QQ)
x^2 - 2/3*x + 1
sage: f.polynomial(GF(19))
x^2 + 12*x + 1

Polynomials can be useful for getting the coefficients of an expression:

sage: g = 6*x^2 - 5
sage: g.coefficients()
[[-5, 0], [6, 2]]
sage: g.polynomial(QQ).list()
[-5, 0, 6]
sage: g.polynomial(QQ).dict()
{0: -5, 2: 6}
sage: f = x^2*e + x + pi/e
sage: f.polynomial(RDF)
2.71828182846*x^2 + 1.0*x + 1.15572734979
sage: g = f.polynomial(RR); g
2.71828182845905*x^2 + 1.00000000000000*x + 1.15572734979092
sage: g.parent()
Univariate Polynomial Ring in x over Real Field with 53 bits of precision            
sage: f.polynomial(RealField(100))
2.7182818284590452353602874714*x^2 + 1.0000000000000000000000000000*x + 1.1557273497909217179100931833
sage: f.polynomial(CDF)
2.71828182846*x^2 + 1.0*x + 1.15572734979
sage: f.polynomial(CC)
2.71828182845905*x^2 + 1.00000000000000*x + 1.15572734979092

We coerce a multivariate polynomial with complex symbolic coefficients:

sage: x, y, n = var('x, y, n')
sage: f = pi^3*x - y^2*e - I; f
pi^3*x - y^2*e - I
sage: f.polynomial(CDF)
(-2.71828182846)*y^2 + 31.0062766803*x - 1.0*I
sage: f.polynomial(CC)
(-2.71828182845905)*y^2 + 31.0062766802998*x - 1.00000000000000*I
sage: f.polynomial(ComplexField(70))
(-2.7182818284590452354)*y^2 + 31.006276680299820175*x - 1.0000000000000000000*I

Another polynomial:

sage: f = sum((e*I)^n*x^n for n in range(5)); f
x^4*e^4 - I*x^3*e^3 - x^2*e^2 + I*x*e + 1
sage: f.polynomial(CDF)
54.5981500331*x^4 - 20.0855369232*I*x^3 - 7.38905609893*x^2 + 2.71828182846*I*x + 1.0
sage: f.polynomial(CC)
54.5981500331442*x^4 - 20.0855369231877*I*x^3 - 7.38905609893065*x^2 + 2.71828182845905*I*x + 1.00000000000000

A multivariate polynomial over a finite field:

sage: f = (3*x^5 - 5*y^5)^7; f
(3*x^5 - 5*y^5)^7
sage: g = f.polynomial(GF(7)); g
3*x^35 + 2*y^35
sage: parent(g)
Multivariate Polynomial Ring in x, y over Finite Field of size 7
power_series()

Return algebraic power series associated to this symbolic expression, which must be a polynomial in one variable, with coefficients coercible to the base ring.

The power series is truncated one more than the degree.

EXAMPLES:

sage: theta = var('theta')
sage: f = theta^3 + (1/3)*theta - 17/3
sage: g = f.power_series(QQ); g
-17/3 + 1/3*theta + theta^3 + O(theta^4)
sage: g^3
-4913/27 + 289/9*theta - 17/9*theta^2 + 2602/27*theta^3 + O(theta^4)
sage: g.parent()
Power Series Ring in theta over Rational Field
pyobject()

Get the underlying Python object corresponding to this expression, assuming this expression is a single numerical value. Otherwise, a TypeError is raised.

EXAMPLES:

sage: var('x')
x
sage: b = -17/3
sage: a = SR(b)
sage: a.pyobject()
-17/3
sage: a.pyobject() is b
True
radical_simplify()

Simplifies this symbolic expression, which can contain logs, exponentials, and radicals, by converting it into a form which is canonical over a large class of expressions and a given ordering of variables

DETAILS: This uses the Maxima radcan() command. From the Maxima documentation: “All functionally equivalent forms are mapped into a unique form. For a somewhat larger class of expressions, produces a regular form. Two equivalent expressions in this class do not necessarily have the same appearance, but their difference can be simplified by radcan to zero. For some expressions radcan is quite time consuming. This is the cost of exploring certain relationships among the components of the expression for simplifications based on factoring and partial fraction expansions of exponents.”

ALIAS: radical_simplify, simplify_radical, simplify_log, log_simplify, exp_simplify, simplify_exp are all the same

EXAMPLES:

sage: var('x,y,a')
(x, y, a)
sage: f = log(x*y)
sage: f.simplify_radical()
log(x) + log(y)
sage: f = (log(x+x^2)-log(x))^a/log(1+x)^(a/2)
sage: f.simplify_radical()
log(x + 1)^(1/2*a)
sage: f = (e^x-1)/(1+e^(x/2))
sage: f.simplify_exp()
e^(1/2*x) - 1
rational_expand()

Expand this symbolic expression. Products of sums and exponentiated sums are multiplied out, numerators of rational expressions which are sums are split into their respective terms, and multiplications are distributed over addition at all levels.

EXAMPLES:

We expand the expression (x-y)^5 using both method and functional notation.

sage: x,y = var('x,y')
sage: a = (x-y)^5
sage: a.expand()
x^5 - 5*x^4*y + 10*x^3*y^2 - 10*x^2*y^3 + 5*x*y^4 - y^5
sage: expand(a)
x^5 - 5*x^4*y + 10*x^3*y^2 - 10*x^2*y^3 + 5*x*y^4 - y^5

We expand some other expressions:

sage: expand((x-1)^3/(y-1))
x^3/(y - 1) - 3*x^2/(y - 1) + 3*x/(y - 1) - 1/(y - 1)
sage: expand((x+sin((x+y)^2))^2)
x^2 + 2*x*sin((x + y)^2) + sin((x + y)^2)^2

We can expand individual sides of a relation:

sage: a = (16*x-13)^2 == (3*x+5)^2/2
sage: a.expand()
256*x^2 - 416*x + 169 == 9/2*x^2 + 15*x + 25/2
sage: a.expand('left')
256*x^2 - 416*x + 169 == 1/2*(3*x + 5)^2
sage: a.expand('right')
(16*x - 13)^2 == 9/2*x^2 + 15*x + 25/2

TESTS:

sage: var(‘x,y’) (x, y) sage: ((x + (2/3)*y)^3).expand() x^3 + 2*x^2*y + 4/3*x*y^2 + 8/27*y^3 sage: expand( (x*sin(x) - cos(y)/x)^2 ) x^2*sin(x)^2 - 2*sin(x)*cos(y) + cos(y)^2/x^2 sage: f = (x-y)*(x+y); f (x - y)*(x + y) sage: f.expand() x^2 - y^2
rational_simplify()

Simplify by expanding repeatedly rational expressions.

ALIAS: rational_simplify and simplify_rational are the same

EXAMPLES:

sage: f = sin(x/(x^2 + x))
sage: f
sin(x/(x^2 + x))
sage: f.simplify_rational()
sin(1/(x + 1))
sage: f = ((x - 1)^(3/2) - (x + 1)*sqrt(x - 1))/sqrt((x - 1)*(x + 1)); f
((x - 1)^(3/2) - sqrt(x - 1)*(x + 1))/sqrt((x - 1)*(x + 1))
sage: f.simplify_rational()
-2*sqrt(x - 1)/sqrt(x^2 - 1)
real()

Return the real part of this symbolic expression.

EXAMPLES:

sage: x = var('x')
sage: x.real_part()
real_part(x)
sage: SR(2+3*I).real_part()
2
sage: SR(CDF(2,3)).real_part()
2.0
sage: SR(CC(2,3)).real_part()
2.00000000000000

sage: f = log(x)
sage: f.real_part()
log(abs(x))
real_part()

Return the real part of this symbolic expression.

EXAMPLES:

sage: x = var('x')
sage: x.real_part()
real_part(x)
sage: SR(2+3*I).real_part()
2
sage: SR(CDF(2,3)).real_part()
2.0
sage: SR(CC(2,3)).real_part()
2.00000000000000

sage: f = log(x)
sage: f.real_part()
log(abs(x))
rhs()

If self is a relational expression, return the right hand side of the relation. Otherwise, raise a ValueError.

EXAMPLES:

sage: x = var('x')
sage: eqn = (x-1)^2 <= x^2 - 2*x + 3
sage: eqn.right_hand_side()
x^2 - 2*x + 3
sage: eqn.rhs()
x^2 - 2*x + 3
sage: eqn.right()
x^2 - 2*x + 3
right()

If self is a relational expression, return the right hand side of the relation. Otherwise, raise a ValueError.

EXAMPLES:

sage: x = var('x')
sage: eqn = (x-1)^2 <= x^2 - 2*x + 3
sage: eqn.right_hand_side()
x^2 - 2*x + 3
sage: eqn.rhs()
x^2 - 2*x + 3
sage: eqn.right()
x^2 - 2*x + 3
right_hand_side()

If self is a relational expression, return the right hand side of the relation. Otherwise, raise a ValueError.

EXAMPLES:

sage: x = var('x')
sage: eqn = (x-1)^2 <= x^2 - 2*x + 3
sage: eqn.right_hand_side()
x^2 - 2*x + 3
sage: eqn.rhs()
x^2 - 2*x + 3
sage: eqn.right()
x^2 - 2*x + 3
roots()

Returns roots of self that can be found exactly, possibly with multiplicities. Not all roots are guaranteed to be found.

Warning

This is not a numerical solver - use find_root to solve for self == 0 numerically on an interval.

INPUT:

  • x - variable to view the function in terms of (use default variable if not given)
  • explicit_solutions - bool (default True); require that roots be explicit rather than implicit
  • multiplicities - bool (default True); when True, return multiplicities
  • ring - a ring (default None): if not None, convert self to a polynomial over ring and find roots over ring

OUTPUT:

list of pairs (root, multiplicity) or list of roots

If there are infinitely many roots, e.g., a function like \sin(x), only one is returned.

EXAMPLES:

sage: var('x, a')
(x, a)

A simple example:

sage: ((x^2-1)^2).roots()
[(-1, 2), (1, 2)]
sage: ((x^2-1)^2).roots(multiplicities=False)
[-1, 1]

A complicated example.

sage: f = expand((x^2 - 1)^3*(x^2 + 1)*(x-a)); f
-a*x^8 + x^9 + 2*a*x^6 - 2*x^7 - 2*a*x^2 + 2*x^3 + a - x

The default variable is a, since it is the first in alphabetical order:

sage: f.roots()
[(x, 1)]

As a polynomial in a, x is indeed a root:

sage: f.poly(a)
x^9 - 2*x^7 + 2*x^3 - (x^8 - 2*x^6 + 2*x^2 - 1)*a - x
sage: f(a=x)
0

The roots in terms of x are what we expect:

sage: f.roots(x)
[(a, 1), (-I, 1), (I, 1), (1, 3), (-1, 3)]

Only one root of \sin(x) = 0 is given:

sage: f = sin(x)    
sage: f.roots(x)
[(0, 1)]

We derive the roots of a general quadratic polynomial:

sage: var('a,b,c,x')
(a, b, c, x)
sage: (a*x^2 + b*x + c).roots(x)
[(-1/2*(b + sqrt(-4*a*c + b^2))/a, 1), (-1/2*(b - sqrt(-4*a*c + b^2))/a, 1)]

By default, all the roots are required to be explicit rather than implicit. To get implicit roots, pass explicit_solutions=False to .roots()

sage: var('x')
x
sage: f = x^(1/9) + (2^(8/9) - 2^(1/9))*(x - 1) - x^(8/9)
sage: f.roots()
...
RuntimeError: no explicit roots found
sage: f.roots(explicit_solutions=False)
[((2^(8/9) - 2^(1/9) + x^(8/9) - x^(1/9))/(2^(8/9) - 2^(1/9)), 1)]

Another example, but involving a degree 5 poly whose roots don’t get computed explicitly:

sage: f = x^5 + x^3 + 17*x + 1
sage: f.roots()
...
RuntimeError: no explicit roots found
sage: f.roots(explicit_solutions=False)
[(x^5 + x^3 + 17*x + 1, 1)]
sage: f.roots(explicit_solutions=False, multiplicities=False)
[x^5 + x^3 + 17*x + 1]

Now let’s find some roots over different rings:

sage: f.roots(ring=CC)
[(-0.0588115223184495, 1), (-1.331099917875... - 1.52241655183732*I, 1), (-1.331099917875... + 1.52241655183732*I, 1), (1.36050567903502 - 1.51880872209965*I, 1), (1.36050567903502 + 1.51880872209965*I, 1)]
sage: (2.5*f).roots(ring=RR)
[(-0.058811522318449..., 1)]
sage: f.roots(ring=CC, multiplicities=False)
[-0.0588115223184495, -1.331099917875... - 1.52241655183732*I, -1.331099917875... + 1.52241655183732*I, 1.36050567903502 - 1.51880872209965*I, 1.36050567903502 + 1.51880872209965*I]
sage: f.roots(ring=QQ)
[]
sage: f.roots(ring=QQbar, multiplicities=False)
[-0.05881152231844944?, -1.331099917875796? - 1.522416551837318?*I, -1.331099917875796? + 1.522416551837318?*I, 1.360505679035020? - 1.518808722099650?*I, 1.360505679035020? + 1.518808722099650?*I]

Root finding over finite fields:

sage: f.roots(ring=GF(7^2, 'a'))
[(3, 1), (4*a + 6, 2), (3*a + 3, 2)]

TESTS:

sage: (sqrt(3) * f).roots(ring=QQ)
...
TypeError: unable to convert sqrt(3) to a rational
series()

Return the power series expansion of self in terms of the variable symbol to the given order.

INPUT:

  • symbol - a variable
  • order - an integer

OUTPUT:

  • a power series

To truncate the power series and obtain a normal expression, use the truncate command.

EXAMPLES:

We expand a polynomial in x about 0, about 1, and also truncate it back to a polynomial:

sage: var('x,y')
(x, y)
sage: f = (x^3 - sin(y)*x^2 - 5*x + 3); f
x^3 - x^2*sin(y) - 5*x + 3
sage: g = f.series(x, 4); g
3 + (-5)*x + (-sin(y))*x^2 + 1*x^3
sage: g.truncate()
x^3 - x^2*sin(y) - 5*x + 3
sage: g = f.series(x==1, 4); g
(-sin(y) - 1) + (-2*sin(y) - 2)*(x - 1) + (-sin(y) + 3)*(x - 1)^2 + 1*(x - 1)^3
sage: h = g.truncate(); h
-(sin(y) - 3)*(x - 1)^2 + (x - 1)^3 - 2*(sin(y) + 1)*(x - 1) - sin(y) - 1
sage: h.expand()
x^3 - x^2*sin(y) - 5*x + 3

We computer another series expansion of an analytic function:

sage: f = sin(x)/x^2
sage: f.series(x,7)
1*x^(-1) + (-1/6)*x + 1/120*x^3 + (-1/5040)*x^5 + Order(x^7)
sage: f.series(x==1,3)
(sin(1)) + (-2*sin(1) + cos(1))*(x - 1) + (5/2*sin(1) - 2*cos(1))*(x - 1)^2 + Order((x - 1)^3)
sage: f.series(x==1,3).truncate().expand()
5/2*x^2*sin(1) - 2*x^2*cos(1) - 7*x*sin(1) + 5*x*cos(1) + 11/2*sin(1) - 3*cos(1)

Following the GiNaC tutorial, we use John Machin’s amazing formula \pi = 16 \tan^{-1}(1/5) - 4 \tan^{-1}(1/239) to compute digits of \pi. We expand the arc tangent around 0 and insert the fractions 1/5 and 1/239.

sage: x = var('x')
sage: f = atan(x).series(x, 10); f
1*x + (-1/3)*x^3 + 1/5*x^5 + (-1/7)*x^7 + 1/9*x^9 + Order(x^10)
sage: float(16*f.subs(x==1/5) - 4*f.subs(x==1/239))
3.1415926824043994
show()

Show this symbolic expression, i.e., typeset it nicely.

EXAMPLES:

sage: (x^2 + 1).show()
x^{2}  + 1
simplify()

Returns a simplified version of this symbolic expression.

Note

Currently, this does just sends the expression to Maxima and converts it back to Sage.

EXAMPLES:

sage: a = var('a'); f = x*sin(2)/(x^a); f
x*sin(2)/x^a
sage: f.simplify()
x^(-a + 1)*sin(2)
simplify_exp()

Simplifies this symbolic expression, which can contain logs, exponentials, and radicals, by converting it into a form which is canonical over a large class of expressions and a given ordering of variables

DETAILS: This uses the Maxima radcan() command. From the Maxima documentation: “All functionally equivalent forms are mapped into a unique form. For a somewhat larger class of expressions, produces a regular form. Two equivalent expressions in this class do not necessarily have the same appearance, but their difference can be simplified by radcan to zero. For some expressions radcan is quite time consuming. This is the cost of exploring certain relationships among the components of the expression for simplifications based on factoring and partial fraction expansions of exponents.”

ALIAS: radical_simplify, simplify_radical, simplify_log, log_simplify, exp_simplify, simplify_exp are all the same

EXAMPLES:

sage: var('x,y,a')
(x, y, a)
sage: f = log(x*y)
sage: f.simplify_radical()
log(x) + log(y)
sage: f = (log(x+x^2)-log(x))^a/log(1+x)^(a/2)
sage: f.simplify_radical()
log(x + 1)^(1/2*a)
sage: f = (e^x-1)/(1+e^(x/2))
sage: f.simplify_exp()
e^(1/2*x) - 1
simplify_full()

Applies simplify_trig, simplify_rational, and simplify_radical to self (in that order).

ALIAS: simplify_full and full_simplify are the same.

EXAMPLES:

sage: a = log(8)/log(2)
sage: a.simplify_full()
3
sage: f = sin(x)^2 + cos(x)^2
sage: f.simplify_full()
1
sage: f = sin(x/(x^2 + x))
sage: f.simplify_full()
sin(1/(x + 1))
simplify_log()

Simplifies this symbolic expression, which can contain logs, exponentials, and radicals, by converting it into a form which is canonical over a large class of expressions and a given ordering of variables

DETAILS: This uses the Maxima radcan() command. From the Maxima documentation: “All functionally equivalent forms are mapped into a unique form. For a somewhat larger class of expressions, produces a regular form. Two equivalent expressions in this class do not necessarily have the same appearance, but their difference can be simplified by radcan to zero. For some expressions radcan is quite time consuming. This is the cost of exploring certain relationships among the components of the expression for simplifications based on factoring and partial fraction expansions of exponents.”

ALIAS: radical_simplify, simplify_radical, simplify_log, log_simplify, exp_simplify, simplify_exp are all the same

EXAMPLES:

sage: var('x,y,a')
(x, y, a)
sage: f = log(x*y)
sage: f.simplify_radical()
log(x) + log(y)
sage: f = (log(x+x^2)-log(x))^a/log(1+x)^(a/2)
sage: f.simplify_radical()
log(x + 1)^(1/2*a)
sage: f = (e^x-1)/(1+e^(x/2))
sage: f.simplify_exp()
e^(1/2*x) - 1
simplify_radical()

Simplifies this symbolic expression, which can contain logs, exponentials, and radicals, by converting it into a form which is canonical over a large class of expressions and a given ordering of variables

DETAILS: This uses the Maxima radcan() command. From the Maxima documentation: “All functionally equivalent forms are mapped into a unique form. For a somewhat larger class of expressions, produces a regular form. Two equivalent expressions in this class do not necessarily have the same appearance, but their difference can be simplified by radcan to zero. For some expressions radcan is quite time consuming. This is the cost of exploring certain relationships among the components of the expression for simplifications based on factoring and partial fraction expansions of exponents.”

ALIAS: radical_simplify, simplify_radical, simplify_log, log_simplify, exp_simplify, simplify_exp are all the same

EXAMPLES:

sage: var('x,y,a')
(x, y, a)
sage: f = log(x*y)
sage: f.simplify_radical()
log(x) + log(y)
sage: f = (log(x+x^2)-log(x))^a/log(1+x)^(a/2)
sage: f.simplify_radical()
log(x + 1)^(1/2*a)
sage: f = (e^x-1)/(1+e^(x/2))
sage: f.simplify_exp()
e^(1/2*x) - 1
simplify_rational()

Simplify by expanding repeatedly rational expressions.

ALIAS: rational_simplify and simplify_rational are the same

EXAMPLES:

sage: f = sin(x/(x^2 + x))
sage: f
sin(x/(x^2 + x))
sage: f.simplify_rational()
sin(1/(x + 1))
sage: f = ((x - 1)^(3/2) - (x + 1)*sqrt(x - 1))/sqrt((x - 1)*(x + 1)); f
((x - 1)^(3/2) - sqrt(x - 1)*(x + 1))/sqrt((x - 1)*(x + 1))
sage: f.simplify_rational()
-2*sqrt(x - 1)/sqrt(x^2 - 1)
simplify_trig()

First expands using trig_expand, then employs the identities \sin(x)^2 + \cos(x)^2 = 1 and \cosh(x)^2 - \sin(x)^2 = 1 to simplify expressions containing tan, sec, etc., to sin, cos, sinh, cosh.

ALIAS: trig_simplify and simplify_trig are the same

EXAMPLES:

sage: f = sin(x)^2 + cos(x)^2; f
sin(x)^2 + cos(x)^2
sage: f.simplify()
sin(x)^2 + cos(x)^2
sage: f.simplify_trig()
1
sin()

EXAMPLES:

sage: var('x, y')
(x, y)
sage: sin(x^2 + y^2)
sin(x^2 + y^2)
sage: sin(sage.symbolic.constants.pi)
0
sage: sin(SR(1))
sin(1)
sage: sin(SR(RealField(150)(1)))
0.84147098480789650665250232163029899962256306

TESTS:

sage: SR(oo).sin()
...
RuntimeError: sin_eval(): sin(infinity) encountered
sage: SR(-oo).sin()
...
RuntimeError: sin_eval(): sin(infinity) encountered
sage: SR(unsigned_infinity).sin()
...
RuntimeError: sin_eval(): sin(infinity) encountered
sinh()

Return sinh of self.

We have $sinh(x) = (e^{x} - e^{-x})/2$.

EXAMPLES:

sage: x.sinh()
sinh(x)
sage: SR(1).sinh()
sinh(1)
sage: SR(0).sinh()
0
sage: SR(1.0).sinh()
sinh(1.00000000000000)

Use .n() to get a numerical approximation:

sage: SR(1.0).sinh().n()
1.17520119364380
sage: maxima('sinh(1.0)')
1.175201193643801

sinh(1.0000000000000000000000000)
sage: SR(1).sinh().n(90)
1.1752011936438014568823819
sage: SR(RIF(1)).sinh()
sinh(1)
sage: SR(RIF(1)).sinh().n()
1.175201193643802?

TESTS:

sage: SR(oo).sinh()
+Infinity
sage: SR(-oo).sinh()
-Infinity
sage: SR(unsigned_infinity).sinh()
...
RuntimeError: sinh_eval(): sinh(unsigned_infinity) encountered
solve()

Analytically solve the equation self == 0 for the variable x.

Warning

This is not a numerical solver - use find_root to solve for self == 0 numerically on an interval.

INPUT:

  • x - variable to solve for

  • multiplicities - bool (default: False); if True, return corresponding multiplicities.

  • explicit_solutions - bool; if True, require that all

    solutions returned be explicit (rather than implicit)

EXAMPLES:

sage: z = var('z')
sage: (z^5 - 1).solve(z)
[z == e^(2/5*I*pi), z == e^(4/5*I*pi), z == e^(-4/5*I*pi), z == e^(-2/5*I*pi), z == 1]

sage: var('Q')
Q
sage: solve(Q*sqrt(Q^2 + 2) - 1,Q)
[Q == 1/sqrt(-sqrt(2) + 1), Q == 1/sqrt(sqrt(2) + 1)]
sqrt()
EXAMPLES:
sage: var(‘x, y’) (x, y) sage: SR(2).sqrt() sqrt(2) sage: (x^2+y^2).sqrt() sqrt(x^2 + y^2) sage: (x^2).sqrt() sqrt(x^2)
step()

Return the value of the Heaviside step function, which is 0 for negative x, 1/2 for 0, and 1 for positive x.

EXAMPLES:

sage: x = var('x')
sage: SR(1.5).step()
1
sage: SR(0).step()
1/2
sage: SR(-1/2).step()
0
sage: SR(float(-1)).step()
0
subs()

EXAMPLES:

sage: var('x,y,z,a,b,c,d,e,f')
(x, y, z, a, b, c, d, e, f)
sage: w0 = SR.wild(0); w1 = SR.wild(1)
sage: t = a^2 + b^2 + (x+y)^3

# substitute with keyword arguments (works only with symbols)
sage: t.subs(a=c)
(x + y)^3 + b^2 + c^2

# substitute with a dictionary argument
sage: t.subs({a^2: c})
(x + y)^3 + b^2 + c

sage: t.subs({w0^2: w0^3})
(x + y)^3 + a^3 + b^3

# substitute with a relational expression
sage: t.subs(w0^2 == w0^3)
(x + y)^3 + a^3 + b^3

sage: t.subs(w0==w0^2)
(x^2 + y^2)^18 + a^16 + b^16           

# more than one keyword argument is accepted
sage: t.subs(a=b, b=c)
(x + y)^3 + b^2 + c^2

# using keyword arguments with a dictionary is allowed
sage: t.subs({a:b}, b=c)
(x + y)^3 + b^2 + c^2

# in this case keyword arguments override the dictionary
sage: t.subs({a:b}, a=c)
(x + y)^3 + b^2 + c^2

sage: t.subs({a:b, b:c})
(x + y)^3 + b^2 + c^2
TESTS:

# no arguments return the same expression sage: t.subs() (x + y)^3 + a^2 + b^2

# similarly for an empty dictionary argument sage: t.subs({}) (x + y)^3 + a^2 + b^2

# non keyword or dictionary argument returns error sage: t.subs(5) Traceback (most recent call last): ... TypeError: subs takes either a set of keyword arguments, a dictionary, or a symbolic relational expression

# substitutions with infinity sage: (x/y).subs(y=oo) 0 sage: (x/y).subs(x=oo) +Infinity sage: (x*y).subs(x=oo) +Infinity sage: (x^y).subs(x=oo) Traceback (most recent call last): ... RuntimeError: power::eval(): pow(Infinity, x) for non numeric x is not defined. sage: (x^y).subs(y=oo) Traceback (most recent call last): ... RuntimeError: power::eval(): pow(x, Infinity) for non numeric x is not defined. sage: (x+y).subs(x=oo) +Infinity sage: (x-y).subs(y=oo) -Infinity sage: gamma(x).subs(x=-1) Infinity sage: 1/gamma(x).subs(x=-1) 0

# verify that this operation does not modify the passed dictionary (#6622) sage: var(‘v t’) (v, t) sage: f = v*t sage: D = {v: 2} sage: f(D, t=3) 6 sage: D {v: 2}

subs_expr()

Given a dictionary of key:value pairs, substitute all occurrences of key for value in self. The substitutions can also be given as a number of symbolic equalities key == value; see the examples.

Warning

This is a formal pattern substitution, which may or may not have any mathematical meaning. The exact rules used at present in Sage are determined by Maxima’s subst command. Sometimes patterns are not replaced even though one would think they should be - see examples below.

EXAMPLES:

sage: f = x^2 + 1
sage: f.subs_expr(x^2 == x)
x + 1
sage: var('x,y,z'); f = x^3 + y^2 + z
(x, y, z)
sage: f.subs_expr(x^3 == y^2, z == 1)
2*y^2 + 1

Or the same thing giving the substitutions as a dictionary:

sage: f.subs_expr({x^3:y^2, z:1})
2*y^2 + 1

sage: f = x^2 + x^4
sage: f.subs_expr(x^2 == x)
x^4 + x
sage: f = cos(x^2) + sin(x^2)
sage: f.subs_expr(x^2 == x)
sin(x) + cos(x)
sage: f(x,y,t) = cos(x) + sin(y) + x^2 + y^2 + t
sage: f.subs_expr(y^2 == t)
(x, y, t) |--> x^2 + 2*t + sin(y) + cos(x)

The following seems really weird, but it is what Maple does:

sage: f.subs_expr(x^2 + y^2 == t)
(x, y, t) |--> x^2 + y^2 + t + sin(y) + cos(x)
sage: maple.eval('subs(x^2 + y^2 = t, cos(x) + sin(y) + x^2 + y^2 + t)')          # optional requires maple
'cos(x)+sin(y)+x^2+y^2+t'
sage: maxima.quit()
sage: maxima.eval('cos(x) + sin(y) + x^2 + y^2 + t, x^2 + y^2 = t')
'sin(y)+y^2+cos(x)+x^2+t'

Actually Mathematica does something that makes more sense:

sage: mathematica.eval('Cos[x] + Sin[y] + x^2 + y^2 + t /. x^2 + y^2 -> t')       # optional -- requires mathematica
2 t + Cos[x] + Sin[y]
substitute()

EXAMPLES:

sage: var('x,y,z,a,b,c,d,e,f')
(x, y, z, a, b, c, d, e, f)
sage: w0 = SR.wild(0); w1 = SR.wild(1)
sage: t = a^2 + b^2 + (x+y)^3

# substitute with keyword arguments (works only with symbols)
sage: t.subs(a=c)
(x + y)^3 + b^2 + c^2

# substitute with a dictionary argument
sage: t.subs({a^2: c})
(x + y)^3 + b^2 + c

sage: t.subs({w0^2: w0^3})
(x + y)^3 + a^3 + b^3

# substitute with a relational expression
sage: t.subs(w0^2 == w0^3)
(x + y)^3 + a^3 + b^3

sage: t.subs(w0==w0^2)
(x^2 + y^2)^18 + a^16 + b^16           

# more than one keyword argument is accepted
sage: t.subs(a=b, b=c)
(x + y)^3 + b^2 + c^2

# using keyword arguments with a dictionary is allowed
sage: t.subs({a:b}, b=c)
(x + y)^3 + b^2 + c^2

# in this case keyword arguments override the dictionary
sage: t.subs({a:b}, a=c)
(x + y)^3 + b^2 + c^2

sage: t.subs({a:b, b:c})
(x + y)^3 + b^2 + c^2
TESTS:

# no arguments return the same expression sage: t.subs() (x + y)^3 + a^2 + b^2

# similarly for an empty dictionary argument sage: t.subs({}) (x + y)^3 + a^2 + b^2

# non keyword or dictionary argument returns error sage: t.subs(5) Traceback (most recent call last): ... TypeError: subs takes either a set of keyword arguments, a dictionary, or a symbolic relational expression

# substitutions with infinity sage: (x/y).subs(y=oo) 0 sage: (x/y).subs(x=oo) +Infinity sage: (x*y).subs(x=oo) +Infinity sage: (x^y).subs(x=oo) Traceback (most recent call last): ... RuntimeError: power::eval(): pow(Infinity, x) for non numeric x is not defined. sage: (x^y).subs(y=oo) Traceback (most recent call last): ... RuntimeError: power::eval(): pow(x, Infinity) for non numeric x is not defined. sage: (x+y).subs(x=oo) +Infinity sage: (x-y).subs(y=oo) -Infinity sage: gamma(x).subs(x=-1) Infinity sage: 1/gamma(x).subs(x=-1) 0

# verify that this operation does not modify the passed dictionary (#6622) sage: var(‘v t’) (v, t) sage: f = v*t sage: D = {v: 2} sage: f(D, t=3) 6 sage: D {v: 2}

substitute_expression()

Given a dictionary of key:value pairs, substitute all occurrences of key for value in self. The substitutions can also be given as a number of symbolic equalities key == value; see the examples.

Warning

This is a formal pattern substitution, which may or may not have any mathematical meaning. The exact rules used at present in Sage are determined by Maxima’s subst command. Sometimes patterns are not replaced even though one would think they should be - see examples below.

EXAMPLES:

sage: f = x^2 + 1
sage: f.subs_expr(x^2 == x)
x + 1
sage: var('x,y,z'); f = x^3 + y^2 + z
(x, y, z)
sage: f.subs_expr(x^3 == y^2, z == 1)
2*y^2 + 1

Or the same thing giving the substitutions as a dictionary:

sage: f.subs_expr({x^3:y^2, z:1})
2*y^2 + 1

sage: f = x^2 + x^4
sage: f.subs_expr(x^2 == x)
x^4 + x
sage: f = cos(x^2) + sin(x^2)
sage: f.subs_expr(x^2 == x)
sin(x) + cos(x)
sage: f(x,y,t) = cos(x) + sin(y) + x^2 + y^2 + t
sage: f.subs_expr(y^2 == t)
(x, y, t) |--> x^2 + 2*t + sin(y) + cos(x)

The following seems really weird, but it is what Maple does:

sage: f.subs_expr(x^2 + y^2 == t)
(x, y, t) |--> x^2 + y^2 + t + sin(y) + cos(x)
sage: maple.eval('subs(x^2 + y^2 = t, cos(x) + sin(y) + x^2 + y^2 + t)')          # optional requires maple
'cos(x)+sin(y)+x^2+y^2+t'
sage: maxima.quit()
sage: maxima.eval('cos(x) + sin(y) + x^2 + y^2 + t, x^2 + y^2 = t')
'sin(y)+y^2+cos(x)+x^2+t'

Actually Mathematica does something that makes more sense:

sage: mathematica.eval('Cos[x] + Sin[y] + x^2 + y^2 + t /. x^2 + y^2 -> t')       # optional -- requires mathematica
2 t + Cos[x] + Sin[y]
substitute_function()

Returns this symbolic expressions all occurrences of the function original replaced with the function new.

EXAMPLES:

sage: x,y = var('x,y')
sage: clear_functions()
sage: foo = function('foo'); bar = function('bar')
sage: f = foo(x) + 1/foo(pi*y)
sage: f.substitute_function(foo, bar)
1/bar(pi*y) + bar(x)
subtract_from_both_sides()

Returns a relation obtained by subtracting x from both sides of this relation.

EXAMPLES:

sage: eqn = x*sin(x)*sqrt(3) + sqrt(2) > cos(sin(x))
sage: eqn.subtract_from_both_sides(sqrt(2))
sqrt(3)*x*sin(x) > -sqrt(2) + cos(sin(x))
sage: eqn.subtract_from_both_sides(cos(sin(x)))
sqrt(3)*x*sin(x) + sqrt(2) - cos(sin(x)) > 0
tan()

EXAMPLES:

sage: var('x, y')
(x, y)
sage: tan(x^2 + y^2)
tan(x^2 + y^2)
sage: tan(sage.symbolic.constants.pi/2)
Infinity
sage: tan(SR(1))
tan(1)
sage: tan(SR(RealField(150)(1)))
1.5574077246549022305069748074583601730872508

TESTS:

sage: SR(oo).tan()
...
RuntimeError: tan_eval(): tan(infinity) encountered
sage: SR(-oo).tan()
...
RuntimeError: tan_eval(): tan(infinity) encountered
sage: SR(unsigned_infinity).tan()
...
RuntimeError: tan_eval(): tan(infinity) encountered
tanh()

Return tanh of self.

We have $ anh(x) = sinh(x) / cosh(x)$.

EXAMPLES:

sage: x.tanh()
tanh(x)
sage: SR(1).tanh()
tanh(1)
sage: SR(0).tanh()
0
sage: SR(1.0).tanh()
tanh(1.00000000000000)

Use .n() to get a numerical approximation:

sage: SR(1.0).tanh().n()
0.761594155955765
sage: maxima('tanh(1.0)')
.7615941559557649
sage: plot(lambda x: SR(x).tanh(), -1, 1)

TESTS:

sage: SR(oo).tanh()
1
sage: SR(-oo).tanh()
-1
sage: SR(unsigned_infinity).tanh()
...
RuntimeError: tanh_eval(): tanh(unsigned_infinity) encountered
taylor()

Expands this symbolic expression in a truncated Taylor or Laurent series in the variable v around the point a, containing terms through (x - a)^n.

INPUT:

  • v - variable
  • a - number
  • n - integer

EXAMPLES:

sage: var('a, x, z')
(a, x, z)
sage: taylor(a*log(z), z, 2, 3)
1/24*(z - 2)^3*a - 1/8*(z - 2)^2*a + 1/2*(z - 2)*a + a*log(2)
sage: taylor(sqrt (sin(x) + a*x + 1), x, 0, 3)
1/48*(3*a^3 + 9*a^2 + 9*a - 1)*x^3 - 1/8*(a^2 + 2*a + 1)*x^2 + 1/2*(a + 1)*x + 1
sage: taylor (sqrt (x + 1), x, 0, 5)
7/256*x^5 - 5/128*x^4 + 1/16*x^3 - 1/8*x^2 + 1/2*x + 1
sage: taylor (1/log (x + 1), x, 0, 3)
-19/720*x^3 + 1/24*x^2 - 1/12*x + 1/x + 1/2
sage: taylor (cos(x) - sec(x), x, 0, 5)
-1/6*x^4 - x^2
sage: taylor ((cos(x) - sec(x))^3, x, 0, 9)
-1/2*x^8 - x^6
sage: taylor (1/(cos(x) - sec(x))^3, x, 0, 5)
-15377/7983360*x^4 - 6767/604800*x^2 + 11/120/x^2 + 1/2/x^4 - 1/x^6 - 347/15120
test_relation()

Test this relation at several random values, attempting to find a contradiction. If this relation has no variables, it will also test this relation after casting into the domain.

Because the interval fields never return false positives, we can be assured that if True or False is returned (and proof is False) then the answer is correct.

INPUT:

ntests -- (default 20) the number of iterations to run
domain -- (optional) the domain from which to draw the random values
          defaults to CIF for equality testing and RIF for 
          order testing
proof --  (default True) if False and the domain is an interval field, 
          regard overlapping (potentially equal) intervals as equal,
          and return True if all tests succeeded. 

OUTPUT:

True - this relation holds in the domain and has no variables
False - a contradiction was found
NotImplemented - no contradiction found

EXAMPLES:

sage: (3 < pi).test_relation()
True
sage: (0 >= pi).test_relation()
False
sage: (exp(pi) - pi).n()
19.9990999791895
sage: (exp(pi) - pi == 20).test_relation()
False
sage: (sin(x)^2 + cos(x)^2 == 1).test_relation()
NotImplemented
sage: (sin(x)^2 + cos(x)^2 == 1).test_relation(proof=False)
True
sage: (x == 1).test_relation()
False
sage: var('x,y')
(x, y)
sage: (x < y).test_relation()
False

TESTS:

sage: all_relations = [op for name, op in sorted(operator.__dict__.items()) if len(name) == 2]
sage: all_relations 
[<built-in function eq>, <built-in function ge>, <built-in function gt>, <built-in function le>, <built-in function lt>, <built-in function ne>]
sage: [op(3, pi).test_relation() for op in all_relations]
[False, False, False, True, True, True]
sage: [op(pi, pi).test_relation() for op in all_relations]
[True, True, False, True, False, False]

sage: s = 'some_very_long_variable_name_which_will_definitely_collide_if_we_use_a_reasonable_length_bound_for_a_hash_that_respects_lexicographic_order'
sage: t1, t2 = var(','.join([s+'1',s+'2']))
sage: (t1 == t2).test_relation()
False
trailing_coeff()

Return the trailing coefficient of s in self, i.e., the coefficient of the smallest power of s in self.

EXAMPLES:

sage: var('x,y,a')
(x, y, a)
sage: f = 100 + a*x + x^3*sin(x*y) + x*y + x/y + 2*sin(x*y)/x; f
x^3*sin(x*y) + a*x + x*y + x/y + 2*sin(x*y)/x + 100
sage: f.trailing_coefficient(x)
2*sin(x*y)
sage: f.trailing_coefficient(y)
x
sage: f.trailing_coefficient(sin(x*y))
a*x + x*y + x/y + 100
trailing_coefficient()

Return the trailing coefficient of s in self, i.e., the coefficient of the smallest power of s in self.

EXAMPLES:

sage: var('x,y,a')
(x, y, a)
sage: f = 100 + a*x + x^3*sin(x*y) + x*y + x/y + 2*sin(x*y)/x; f
x^3*sin(x*y) + a*x + x*y + x/y + 2*sin(x*y)/x + 100
sage: f.trailing_coefficient(x)
2*sin(x*y)
sage: f.trailing_coefficient(y)
x
sage: f.trailing_coefficient(sin(x*y))
a*x + x*y + x/y + 100
trig_expand()

Expands trigonometric and hyperbolic functions of sums of angles and of multiple angles occurring in self. For best results, self should already be expanded.

INPUT:

  • full - (default: False) To enhance user control of simplification, this function expands only one level at a time by default, expanding sums of angles or multiple angles. To obtain full expansion into sines and cosines immediately, set the optional parameter full to True.
  • half_angles - (default: False) If True, causes half-angles to be simplified away.
  • plus - (default: True) Controls the sum rule; expansion of sums (e.g. ‘sin(x + y)’) will take place only if plus is True.
  • times - (default: True) Controls the product rule, expansion of products (e.g. sin(2*x)) will take place only if times is True.

OUTPUT: a symbolic expression

EXAMPLES:

sage: sin(5*x).expand_trig()
sin(x)^5 - 10*sin(x)^3*cos(x)^2 + 5*sin(x)*cos(x)^4
sage: cos(2*x + var('y')).expand_trig()
-sin(2*x)*sin(y) + cos(2*x)*cos(y)

We illustrate various options to this function:

sage: f = sin(sin(3*cos(2*x))*x)
sage: f.expand_trig()
sin(-(sin(cos(2*x))^3 - 3*sin(cos(2*x))*cos(cos(2*x))^2)*x)
sage: f.expand_trig(full=True)
sin(((sin(sin(x)^2)*cos(cos(x)^2) - sin(cos(x)^2)*cos(sin(x)^2))^3 - 3*(sin(sin(x)^2)*cos(cos(x)^2) - sin(cos(x)^2)*cos(sin(x)^2))*(sin(sin(x)^2)*sin(cos(x)^2) + cos(sin(x)^2)*cos(cos(x)^2))^2)*x)
sage: sin(2*x).expand_trig(times=False)
sin(2*x)
sage: sin(2*x).expand_trig(times=True)
2*sin(x)*cos(x)
sage: sin(2 + x).expand_trig(plus=False)
sin(x + 2)
sage: sin(2 + x).expand_trig(plus=True)
sin(2)*cos(x) + sin(x)*cos(2)
sage: sin(x/2).expand_trig(half_angles=False)
sin(1/2*x)
sage: sin(x/2).expand_trig(half_angles=True)
1/2*sqrt(-cos(x) + 1)*sqrt(2)*(-1)^floor(1/2*x/pi)

ALIASES:

trig_expand() and expand_trig() are the same

trig_simplify()

First expands using trig_expand, then employs the identities \sin(x)^2 + \cos(x)^2 = 1 and \cosh(x)^2 - \sin(x)^2 = 1 to simplify expressions containing tan, sec, etc., to sin, cos, sinh, cosh.

ALIAS: trig_simplify and simplify_trig are the same

EXAMPLES:

sage: f = sin(x)^2 + cos(x)^2; f
sin(x)^2 + cos(x)^2
sage: f.simplify()
sin(x)^2 + cos(x)^2
sage: f.simplify_trig()
1
truncate()

Given a power series or expression, return the corresponding expression without the big oh.

INPUT:

  • a series as output by the series command

OUTPUT:

  • expression

EXAMPLES:

sage: f = sin(x)/x^2
sage: f.truncate()
sin(x)/x^2
sage: f.series(x,7)
1*x^(-1) + (-1/6)*x + 1/120*x^3 + (-1/5040)*x^5 + Order(x^7)
sage: f.series(x,7).truncate()
-1/5040*x^5 + 1/120*x^3 - 1/6*x + 1/x
sage: f.series(x==1,3).truncate().expand()
5/2*x^2*sin(1) - 2*x^2*cos(1) - 7*x*sin(1) + 5*x*cos(1) + 11/2*sin(1) - 3*cos(1)
variables()

Return sorted list of variables that occur in this expression.

EXAMPLES:

sage: (x,y,z) = var('x,y,z')
sage: (x+y).variables()
(x, y)
sage: (2*x).variables()
(x,)
sage: (x^y).variables()
(x, y)
sage: sin(x+y^z).variables()
(x, y, z)
zeta()

EXAMPLES:

sage: x, y = var('x, y')
sage: (x/y).zeta()
zeta(x/y)
sage: SR(2).zeta()
1/6*pi^2
sage: SR(3).zeta()
zeta(3)
sage: SR(CDF(0,1)).zeta()
zeta(1.0*I)
sage: SR(CDF(0,1)).zeta().n()
0.00330022368532 - 0.418155449141*I
sage: CDF(0,1).zeta()
0.00330022368532 - 0.418155449141*I
sage: plot(lambda x: SR(x).zeta(), -10,10).show(ymin=-3,ymax=3)

TESTS:

sage: t = SR(1).zeta(); t
zeta(1)
sage: t.n()
+infinity
class sage.symbolic.expression.ExpressionIterator
__iter__()

Return this iterator object itself.

EXAMPLES:

sage: x,y,z = var('x,y,z')
sage: i = (x+y).iterator()
sage: iter(i) is i
True
static __new__()
T.__new__(S, ...) -> a new object with type S, a subtype of T
__next__()

Return the next component of the expression.

EXAMPLES:

sage: x,y,z = var('x,y,z')
sage: i = (x+y).iterator()
sage: i.next()
x
next()
x.next() -> the next value, or raise StopIteration
sage.symbolic.expression.is_Expression()

Returns True if x is a symbolic Expression.

EXAMPLES:

sage: from sage.symbolic.expression import is_Expression
sage: is_Expression(x)
True
sage: is_Expression(2)
False
sage: is_Expression(SR(2))
True
sage.symbolic.expression.is_SymbolicEquation()

Returns True if x is a symbolic equation.

EXAMPLES:

The following two examples are symbolic equations:

sage: from sage.symbolic.expression import is_SymbolicEquation
sage: is_SymbolicEquation(sin(x) == x)
True
sage: is_SymbolicEquation(sin(x) < x)
True
sage: is_SymbolicEquation(x)
False

This is not, since 2==3 evaluates to the boolean False:

sage: is_SymbolicEquation(2 == 3)
False

However here since both 2 and 3 are coerced to be symbolic, we obtain a symbolic equation:

sage: is_SymbolicEquation(SR(2) == SR(3))
True

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