Derivative of Arcsecant Function/Corollary 1

Corollary to Derivative of Arcsecant Function
Let $x \in \R$.

Let $\operatorname{arcsec} \left({\dfrac x a}\right)$ be the arccotangent of $\dfrac x a$.

Then:
 * $\dfrac {\mathrm d \left({\operatorname{arcsec} \left({\frac x a}\right) }\right)} {\mathrm d x} = \dfrac a {\left\vert{x}\right\vert {\sqrt {x^2 - a^2} } }$