Derivative
@[@
\begin{array}{lcr}
\R{atan}^{(1)} (x) & = & \frac{1}{1 + x^2}
\end{array}
@]@ Example
The file
atan.cpp
contains an example and test of this function.
It returns true if it succeeds and false otherwise.
Input File: cppad/core/std_math_98.hpp