\subsection{acosh}
\label{labacosh}
\noindent Name: \textbf{acosh}\\
\phantom{aaa}the arg-hyperbolic cosine function.\\[0.2cm]
\noindent Library names:\\
\verb|   sollya_obj_t sollya_lib_acosh(sollya_obj_t)|\\
\verb|   sollya_obj_t sollya_lib_build_function_acosh(sollya_obj_t)|\\
\verb|   #define SOLLYA_ACOSH(x) sollya_lib_build_function_acosh(x)|\\[0.2cm]
\noindent Description: \begin{itemize}

\item \textbf{acosh} is the inverse of the function \textbf{cosh}: \textbf{acosh}(y) is the unique number 
   $x \in [0; +\infty]$ such that \textbf{cosh}(x)=y.

\item It is defined only for $y \in [0;+\infty]$.
\end{itemize}
See also: \textbf{cosh} (\ref{labcosh})
