Status: Accepted
Owner: smichr
Labels: Type-Defect Priority-Medium
New issue 2136 by smichr: polygamma expansion problems
http://code.google.com/p/sympy/issues/detail?id=2136
polygamma needs some attention since the expanded and unexpanded forms give
different results when substituting in a value for x:
h[9] >>> polygamma(0, 2*x).expand(func=True).subs(x, 1)
1 - EulerGamma + log(2)
h[9] >>> polygamma(0, 2*x).subs(x, 1)
1 - EulerGamma
The docstring doesn't provide much direction, but wikipedia says that
polygamma(m, z) is the (m+1)th derivative of the log(gamma(z)) wrt z. Does
anyone have an idea what the expansion is trying to give?
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