Primitive of x by Cotangent of a x

Theorem

 * $\displaystyle \int x \cot a x \ \mathrm d x = \frac 1 {a^2} \left({a x - \frac {\left({a x}\right)^3} 9 - \frac {\left({a x}\right)^5} {225} - \cdots - \frac {2^{2 n} B_n \left({a x}\right)^{2 n + 1} } {\left({2 n + 1}\right)!} + \cdots}\right) + C$

where $B_n$ denotes the $n$th Bernoulli number.

Also see

 * Primitive of $x \tan a x$