Status: Accepted
Owner: asmeurer
Labels: Type-Defect Priority-Medium Integration WrongResult
New issue 1987 by asmeurer: Integral(f(x), (x, g(x), h(x))).diff(x)
incorrectly returns 0
http://code.google.com/p/sympy/issues/detail?id=1987
In [1]: i = Integral(f(x), (x, g(x), h(x)))
In [2]: i.diff(x)
Out[2]: 0
In [3]: i = Integral(f(y), (y, g(x), h(x)))
In [4]: i.diff(x)
Out[4]:
d d
──(h(x))⋅f(h(x)) - ──(g(x))⋅f(g(x))
dx dx
The first should be the same as the second, since the integration variable
is completely independent of the final result and shouldn't affect diff.
I'm not surprised that this happens, though, since it is generally
considered bad practice to use the same variable in the limits and as the
integration variable.
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