Derivative of Inverse Hyperbolic Secant

Theorem
Let $S$ denote the half-open real interval:
 * $S := \left({0 \,.\,.\, 1}\right]$

Let $x \in S$.

Let $\operatorname{sech}^{-1} x$ be the inverse hyperbolic secant of $x$.

Then:
 * $\dfrac {\mathrm d}{\mathrm d x} \left({\operatorname{sech}^{-1} x}\right) = \dfrac {-1} {x \sqrt{1 - x^2} }$