-------------------------------------------------
lines 10-68 of file: include/cppad/core/atan2.hpp
-------------------------------------------------

{xrst_begin atan2}

AD Two Argument Inverse Tangent Function
########################################

Syntax
******
| *theta* = ``atan2`` ( *y* , *x* )

Purpose
*******
Determines an angle :math:`\theta \in [ - \pi , + \pi ]`
such that

.. math::
   :nowrap:

   \begin{eqnarray}
      \sin ( \theta )  & = & y / \sqrt{ x^2 + y^2 }  \\
      \cos ( \theta )  & = & x / \sqrt{ x^2 + y^2 }
   \end{eqnarray}

y
*
The argument *y* has one of the following prototypes

| |tab| ``const AD`` < *Base* >               & *y*
| |tab| ``const VecAD`` < *Base* >:: ``reference &`` *y*

x
*
The argument *x* has one of the following prototypes

| |tab| ``const AD`` < *Base* >               & *x*
| |tab| ``const VecAD`` < *Base* >:: ``reference &`` *x*

theta
*****
The result *theta* has prototype

   ``AD`` < *Base* > *theta*

Operation Sequence
******************
The AD of *Base*
operation sequence used to calculate *theta* is
:ref:`glossary@Operation@Independent`
of *x* and *y* .

Example
*******
{xrst_toc_hidden
   example/general/atan2.cpp
}
The file
:ref:`atan2.cpp-name`
contains an example and test of this function.

{xrst_end atan2}