Status: Valid
Owner: ----
Labels: Type-Defect Priority-Medium Simplify
New issue 3730 by [email protected]: cancel should work with primitive of
expression
http://code.google.com/p/sympy/issues/detail?id=3730
An expression `z` was obtained as follows:
# eq = q*x + q/4 + x**4 + x**3 + 2*x**2 - S(1)/3
# z = eq.subs(x, solve(eq, x)[0])
z = (q*(-sqrt(-2*(-(q - S(7)/8)**S(2)/8 - S(2197)/13824)**(S(1)/3) -
S(13)/12)/2 - sqrt((2*q - S(7)/4)/sqrt(-2*(-(q - S(7)/8)**S(2)/8 -
S(2197)/13824)**(S(1)/3) - S(13)/12) + 2*(-(q - S(7)/8)**S(2)/8 -
S(2197)/13824)**(S(1)/3) - S(13)/6)/2 - S(1)/4) + q/4 + (-sqrt(-2*(-(q
- S(7)/8)**S(2)/8 - S(2197)/13824)**(S(1)/3) - S(13)/12)/2 - sqrt((2*q
- S(7)/4)/sqrt(-2*(-(q - S(7)/8)**S(2)/8 - S(2197)/13824)**(S(1)/3) -
S(13)/12) + 2*(-(q - S(7)/8)**S(2)/8 - S(2197)/13824)**(S(1)/3) -
S(13)/6)/2 - S(1)/4)**4 + (-sqrt(-2*(-(q - S(7)/8)**S(2)/8 -
S(2197)/13824)**(S(1)/3) - S(13)/12)/2 - sqrt((2*q -
S(7)/4)/sqrt(-2*(-(q - S(7)/8)**S(2)/8 - S(2197)/13824)**(S(1)/3) -
S(13)/12) + 2*(-(q - S(7)/8)**S(2)/8 - S(2197)/13824)**(S(1)/3) -
S(13)/6)/2 - S(1)/4)**3 + 2*(-sqrt(-2*(-(q - S(7)/8)**S(2)/8 -
S(2197)/13824)**(S(1)/3) - S(13)/12)/2 - sqrt((2*q -
S(7)/4)/sqrt(-2*(-(q - S(7)/8)**S(2)/8 - S(2197)/13824)**(S(1)/3) -
S(13)/12) + 2*(-(q - S(7)/8)**S(2)/8 - S(2197)/13824)**(S(1)/3) -
S(13)/6)/2 - S(1)/4)**2 - S(1)/3)
It is identically zero but this is not seen unless the primitive is used
with cancel and simplify:
cancel(z)==0
False
simplify(z)==0
False
simplify(cancel(z))==0
False
p=z.as_content_primitive()[1]
cancel(p)==0
False
simplify(p)==0
False
simplify(cancel(p))==0
True
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