I'm trying to calculate the integral of ln(x-y) dy (with x and y complex)
>> integrate(ln(x-y), y)
but sympy gives me
-x*log(-x + y) + y*log(x - y) - y
If I try to differentiate this wrt. y I get
>> diff(-x*log(-x + y) + y*log(x - y) - y, y)
-x/(-x + y) - y/(x - y) + log(x - y) - 1
which is not exactly equal to ln(x-y).
As far as I know the result of the integration should be -ln(x - y)*(x - y)
+ x - y, which also gives the correct result when differentiated in sympy
>> diff(-ln(x-y)*(x-y)+x-y, y)
log(x - y)
The calculations can be seen as a IPython Notebook here
http://nbviewer.ipython.org/gist/FSund/2a49222b54fa95ccdbc0
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