Status: New
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Labels: Type-Defect Priority-Medium

New issue 2849 by [email protected]: integration of cos(x)/sin(x)**n
http://code.google.com/p/sympy/issues/detail?id=2849

The result of integrate(cos(x)/sin(x)**n, x) is
"nice", if n is even, and "ugly", if n is odd
(n is an integer, greater than 1).

Moreover, if n is odd, then diff(integrate(cos(x)/sin(x)**n, x), x)
gives a very ugly expression that cannot be converted back to
cos(x)/sin(x)**n by simplify.

Example:
In [136]: diff(integrate(cos(x)/sin(x)**7, x), x)
             5                   3
36⋅sin(x)⋅cos (x) - 72⋅sin(x)⋅cos (x) + 36⋅sin(x)⋅cos(x)
────────────────────────────────────────────────────────
                                                2
       ⎛     6            4            2       ⎞
       ⎝6⋅cos (x) - 18⋅cos (x) + 18⋅cos (x) - 6⎠

Gabor Takacs


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