\subsection{atan}
\label{labatan}
\noindent Name: \textbf{atan}\\
\phantom{aaa}the arctangent function.\\[0.2cm]
\noindent Library names:\\
\verb|   sollya_obj_t sollya_lib_atan(sollya_obj_t)|\\
\verb|   sollya_obj_t sollya_lib_build_function_atan(sollya_obj_t)|\\
\verb|   #define SOLLYA_ATAN(x) sollya_lib_build_function_atan(x)|\\[0.2cm]
\noindent Description: \begin{itemize}

\item \textbf{atan} is the inverse of the function \textbf{tan}: \textbf{atan}($y$) is the unique number 
   $x \in [-\pi/2; +\pi/2]$ such that \textbf{tan}($x$)=$y$.

\item It is defined for every real number y.
\end{itemize}
See also: \textbf{tan} (\ref{labtan})
