Question Number 154037 by qaz last updated on 13/Sep/21
$$\mathrm{Prove}::\:\:\:\underset{\mathrm{n}=−\infty} {\overset{+\infty} {\sum}}\mathrm{arctan}\:\left(\frac{\mathrm{sinh}\:\mathrm{x}}{\mathrm{cosh}\:\mathrm{n}}\right)=\pi\mathrm{x} \\ $$
Prove-n-arctan-sinh-x-cosh-n-pix-