Derivative of Real Area Hyperbolic Cotangent of x over a/Corollary

Theorem

 * $\map {\dfrac \d {\d x} } {\dfrac 1 {2 a} \map \ln {\dfrac {x + a} {x - a} } } = \dfrac 1 {a^2 - x^2}$

where $\size x > a$.