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<title>Arc tangent of two variables</title>
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<h1 class="refname">atan2</h1>
<p class="verinfo">(PHP 4, PHP 5)</p><p class="refpurpose"><span class="refname">atan2</span> — <span class="dc-title">Arc tangent of two variables</span></p>
</div>
<div class="refsect1 description" id="refsect1-function.atan2-description">
<h3 class="title">Description</h3>
<div class="methodsynopsis dc-description">
<span class="type">float</span> <span class="methodname"><strong>atan2</strong></span>
( <span class="methodparam"><span class="type">float</span> <code class="parameter">$y</code></span>
, <span class="methodparam"><span class="type">float</span> <code class="parameter">$x</code></span>
)</div>
<p class="simpara">
This function calculates the arc tangent of the two variables
<em><code class="parameter">x</code></em> and <em><code class="parameter">y</code></em>. It is
similar to calculating the arc tangent of
<em><code class="parameter">y</code></em> / <em><code class="parameter">x</code></em>, except that
the signs of both arguments are used to determine the quadrant of
the result.
</p>
<p class="simpara">
The function returns the result in radians, which is between -PI
and PI (inclusive).
</p>
</div>
<div class="refsect1 parameters" id="refsect1-function.atan2-parameters">
<h3 class="title">Parameters</h3>
<p class="para">
<dl>
<dt>
<span class="term"><em><code class="parameter">y</code></em></span>
<dd>
<p class="para">
Dividend parameter
</p>
</dd>
</dt>
<dt>
<span class="term"><em><code class="parameter">x</code></em></span>
<dd>
<p class="para">
Divisor parameter
</p>
</dd>
</dt>
</dl>
</p>
</div>
<div class="refsect1 returnvalues" id="refsect1-function.atan2-returnvalues">
<h3 class="title">Return Values</h3>
<p class="para">
The arc tangent of <em><code class="parameter">y</code></em>/<em><code class="parameter">x</code></em>
in radians.
</p>
</div>
<div class="refsect1 seealso" id="refsect1-function.atan2-seealso">
<h3 class="title">See Also</h3>
<p class="para">
<ul class="simplelist">
<li class="member"> <span class="function"><a href="function.atan.html" class="function" rel="rdfs-seeAlso">atan()</a> - Arc tangent</span></li>
</ul>
</p>
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