<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision$ -->
<refentry xml:id="function.atan2" xmlns="http://docbook.org/ns/docbook">
 <refnamediv>
  <refname>atan2</refname>
  <refpurpose>Arc tangent of two variables</refpurpose>
 </refnamediv>
 <refsect1 role="description">
  &reftitle.description;
   <methodsynopsis>
    <type>float</type><methodname>atan2</methodname>
    <methodparam><type>float</type><parameter>y</parameter></methodparam>
    <methodparam><type>float</type><parameter>x</parameter></methodparam>
   </methodsynopsis>
  <simpara>
   This function calculates the arc tangent of the two variables
   <parameter>x</parameter> and <parameter>y</parameter>.  It is
   similar to calculating the arc tangent of
   <parameter>y</parameter> / <parameter>x</parameter>, except that
   the signs of both arguments are used to determine the quadrant of
   the result.
  </simpara>
  <simpara>
   The function returns the result in radians, which is between -PI
   and PI (inclusive).
  </simpara>
 </refsect1>
 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>y</parameter></term>
     <listitem>
      <para>
       Dividend parameter
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>x</parameter></term>
     <listitem>
      <para>
       Divisor parameter
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>
 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   The arc tangent of <parameter>y</parameter>/<parameter>x</parameter> 
   in radians.
  </para>
 </refsect1>
 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><function>atan</function></member>
   </simplelist>
  </para>
 </refsect1>
</refentry>

<!-- Keep this comment at the end of the file
Local variables:
mode: sgml
sgml-omittag:t
sgml-shorttag:t
sgml-minimize-attributes:nil
sgml-always-quote-attributes:t
sgml-indent-step:1
sgml-indent-data:t
indent-tabs-mode:nil
sgml-parent-document:nil
sgml-default-dtd-file:"~/.phpdoc/manual.ced"
sgml-exposed-tags:nil
sgml-local-catalogs:nil
sgml-local-ecat-files:nil
End:
vim600: syn=xml fen fdm=syntax fdl=2 si
vim: et tw=78 syn=sgml
vi: ts=1 sw=1
-->