Status: Accepted
Owner: asmeurer
Labels: Type-Defect Priority-Medium EasyToFix
New issue 2213 by asmeurer: Derivative of Sum
http://code.google.com/p/sympy/issues/detail?id=2213
Sum does not work with diff:
In [223]: Sum(f(x), (x, 1, n)).diff(x)
Out[223]:
d
──(Sum(f(x), (x, 1, n)))
dx
In [224]: Sum(f(x), (x, 1, n)).diff(x).doit()
Out[224]:
d
──(Sum(f(x), (x, 1, n)))
dx
I will have to check my analysis textbooks to see if it is valid to
distribute the derivative when the summation is infinite. But definitely
it should be done for finite sum.
This should be very easy to fix, by the way. Just implement a trivial
_eval_derivative method to Sum.
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