Status: Accepted
Owner: smichr
Labels: Type-Defect Priority-Medium
New issue 2054 by smichr: does factor need to use cancel?
http://code.google.com/p/sympy/issues/detail?id=2054
This seems kind of strange to me. I was testing an "A == B" routine and ran
into a problem with this trig identity:
Here is the expression (which is symbolically identical to 0)
ee = I*(exp(I*x) - exp(-I*x))/(exp(I*x) + exp(-I*x)) - I*(exp(I*x)/2 -
exp(-I*x)/2)/(exp(I*x)/2 + exp(-I*x)/2)
I try to factor the derivative wrt x
factor(ee.diff(x))
-(2 - exp(-2*I*x) - exp(2*I*x))*exp(I*x)/(2*(1 + exp(2*I*x))*(exp(I*x) +
exp(-I*x)))
Hmmm...it factored. Does cancel know that it is zero?
cancel(ee.diff(x))
0
Yes. factor already expands. Perhaps it should cancel an expression, too?
Or is there reason to not do that?
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