Inverse Secant Function

Secant restricted to $[0,\pi]\setminus\left\{\tfrac{\pi}2\right\}$ is a bijection onto its full range $\mathbb{R}\setminus(-1,1)$.

Definition 4.7. $\sec^{-1}:\mathbb{R}\setminus(-1,1)\to[0,\pi]\setminus\left\{\tfrac{\pi}2\right\}$ is defined by $\sec^{-1}(x)=y\iff\sec y=x$ and …