<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "xhtml1-transitional.dtd">
<!-- saved from url=(0013)about:internet -->
<?xml-stylesheet type="text/xsl" href="mathml.xsl"?><html xmlns="http://www.w3.org/1999/xhtml" xmlns:pref="http://www.w3.org/2002/Math/preference" pref:renderer="mathplayer-dl"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><link rel="stylesheet" type="text/css" href="opengl-man.css" /><title>atan - OpenGL ES Shading Language (GLSL ES)</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /></head><body><div class="refentry" title="atan"><a id="radians"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>atan — return the arc-tangent of the parameters</p></div><div class="refsynopsisdiv" title="Declaration"><h2>Declaration</h2><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">genType <b class="fsfunc">atan</b>(</code></td><td>genType <var class="pdparam">y</var>, </td></tr><tr><td> </td><td>genType <var class="pdparam">x</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">genType <b class="fsfunc">atan</b>(</code></td><td>genType <var class="pdparam">y_over_x</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1" title="Parameters"><a id="parameters"></a><h2>Parameters</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>y</code></em></span></dt><dd><p>
                    Specify the numerator of the fraction whose arctangent to return.
                </p></dd><dt><span class="term"><em class="parameter"><code>x</code></em></span></dt><dd><p>
                    Specify the denominator of the fraction whose arctangent to return.
                </p></dd><dt><span class="term"><em class="parameter"><code>y_over_x</code></em></span></dt><dd><p>
                    Specify the fraction whose arctangent to return.
                </p></dd></dl></div></div><div class="refsect1" title="Description"><a id="description"></a><h2>Description</h2><p>
            <code class="function">atan</code> returns the angle whose trigonometric arctangent is
            <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                
                <mml:mfrac>
                    <mml:mrow>
                        <mml:mi mathvariant="italic">y</mml:mi>
                    </mml:mrow>
                    <mml:mrow>
                        <mml:mi mathvariant="italic">x</mml:mi>
                    </mml:mrow>
                </mml:mfrac>
            </mml:math> or <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">y_over_x</mml:mi></mml:math>,
            depending on which overload is invoked. In the first overload, the signs of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">y</mml:mi></mml:math>
            and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">x</mml:mi></mml:math> are used to determine the quadrant
            that the angle lies in. The values returned by <code class="function">atan</code> in this case are in the range
            <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                <mml:list order="numeric">
                    <mml:csymbol encoding="" definitionURL=""><mml:mo>−</mml:mo><mml:pi definitionURL="" encoding=""></mml:pi></mml:csymbol>
                    <mml:pi definitionURL="" encoding=""></mml:pi>
                    </mml:list>
            </mml:math>. Results are undefined if <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">x</mml:mi></mml:math> is zero.
        </p><p>
            For the second overload, <code class="function">atan</code> returns the angle whose tangent is
            <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">y_over_x</mml:mi></mml:math>. Values
            returned in this case are in the range
            <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                <mml:list order="numeric">
                    <mml:mrow>
                        <mml:mo>−</mml:mo>
                        <mml:mfrac>
                            <mml:csymbol encoding="" definitionURL=""><mml:pi definitionURL="" encoding=""></mml:pi></mml:csymbol>
                            <mml:mn>2</mml:mn>
                        </mml:mfrac>
                    </mml:mrow>
                    <mml:mfrac>
                        <mml:pi definitionURL="" encoding=""></mml:pi>
                        <mml:mn>2</mml:mn>
                    </mml:mfrac>
                </mml:list>
            </mml:math>.
        </p></div><div class="refsect1" title="Version Support"><a id="versions"></a><h2>Version Support</h2><div class="informaltable"><table border="1"><colgroup><col align="left" /><col align="center" /><col align="center" /></colgroup><thead><tr><th align="left"><span class="bold"><strong>
                        Function
                        </strong></span></th><th align="left"><span class="bold"><strong>
                        Version 1.00
                        </strong></span></th><th align="left"><span class="bold"><strong>
                        Version 3.00
                        </strong></span></th></tr><tr><th align="left">
                            atan
                        </th><th align="center">
                            <span class="emphasis"><em>Y</em></span>
                        </th><th align="center">
                            <span class="emphasis"><em>Y</em></span>
                        </th></tr></thead></table></div></div><div class="refsect1" title="See Also"><a id="seealso"></a><h2>See Also</h2><p>
            <a class="citerefentry" href="sin.xml"><span class="citerefentry"><span class="refentrytitle">sin</span></span></a>,
            <a class="citerefentry" href="cos.xml"><span class="citerefentry"><span class="refentrytitle">cos</span></span></a>,
            <a class="citerefentry" href="tan.xml"><span class="citerefentry"><span class="refentrytitle">tan</span></span></a>,
            <a class="citerefentry" href="asin.xml"><span class="citerefentry"><span class="refentrytitle">asin</span></span></a>,
            <a class="citerefentry" href="acos.xml"><span class="citerefentry"><span class="refentrytitle">acos</span></span></a>
        </p></div><div class="refsect1" title="Copyright"><a id="Copyright"></a><h2>Copyright</h2><p>
            Copyright <span class="trademark"></span>© 2011-2012 Khronos Group. 
            This material may be distributed subject to the terms and conditions set forth in 
            the Open Publication License, v 1.0, 8 June 1999.
            <a class="ulink" href="http://opencontent.org/openpub/" target="_top">http://opencontent.org/openpub/</a>.
        </p></div></div></body></html>
