Status: Accepted
Owner: ----
Labels: Type-Defect Priority-Medium
New issue 2908 by [email protected]: simplification of polygamma needed
http://code.google.com/p/sympy/issues/detail?id=2908
Although simplify(factorial(x+1)) simplifies nicely to (x + 1)*x!, the
derivative don't simplify so simplify(factorial(x + 1).diff(x) -
((x+1)*factorial(x)).diff(x)) doesn't simplify to zero:
simplify(factorial(x + 1).diff(x) - ((x+1)*factorial(x)).diff(x))
-(x*polygamma(0, x + 1) - x*polygamma(0, x + 2) + polygamma(0, x + 1) -
polygamma(0, x + 2) + 1)*x!
factorial(x + 1).diff(x)
gamma(x + 2)*polygamma(0, x + 2)
((x+1)*factorial(x)).diff(x)
(x + 1)*gamma(x + 1)*polygamma(0, x + 1) + x!
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