Inverse Hyperbolic Cosine

$\begin{figure}\begin{center}\BoxedEPSF{ArcCosh.epsf}\end{center}\end{figure}$

$\begin{figure}\begin{center}\BoxedEPSF{ArcCoshReIm.epsf scaled 700}\end{center}\end{figure}$

The Inverse Function of the Hyperbolic Cosine, denoted $\cosh^{-1}x$ .