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<title>Inverse hyperbolic tangent</title>
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<h1 class="refname">atanh</h1>
<p class="verinfo">(PHP 4 >= 4.1.0, PHP 5)</p><p class="refpurpose"><span class="refname">atanh</span> — <span class="dc-title">Inverse hyperbolic tangent</span></p>
</div>
<div class="refsect1 description" id="refsect1-function.atanh-description">
<h3 class="title">Description</h3>
<div class="methodsynopsis dc-description">
<span class="type">float</span> <span class="methodname"><strong>atanh</strong></span>
( <span class="methodparam"><span class="type">float</span> <code class="parameter">$arg</code></span>
)</div>
<p class="para rdfs-comment">
Returns the inverse hyperbolic tangent of
<em><code class="parameter">arg</code></em>, i.e. the value whose
hyperbolic tangent is <em><code class="parameter">arg</code></em>.
</p>
</div>
<div class="refsect1 parameters" id="refsect1-function.atanh-parameters">
<h3 class="title">Parameters</h3>
<p class="para">
<dl>
<dt>
<span class="term"><em><code class="parameter">arg</code></em></span>
<dd>
<p class="para">
The argument to process
</p>
</dd>
</dt>
</dl>
</p>
</div>
<div class="refsect1 returnvalues" id="refsect1-function.atanh-returnvalues">
<h3 class="title">Return Values</h3>
<p class="para">
Inverse hyperbolic tangent of <em><code class="parameter">arg</code></em>
</p>
</div>
<div class="refsect1 changelog" id="refsect1-function.atanh-changelog">
<h3 class="title">Changelog</h3>
<p class="para">
<table class="doctable informaltable">
<thead>
<tr>
<th>Version</th>
<th>Description</th>
</tr>
</thead>
<tbody class="tbody">
<tr>
<td>5.3.0</td>
<td>
This function is now available on all platforms
</td>
</tr>
</tbody>
</table>
</p>
</div>
<div class="refsect1 seealso" id="refsect1-function.atanh-seealso">
<h3 class="title">See Also</h3>
<p class="para">
<ul class="simplelist">
<li class="member"> <span class="function"><a href="function.tanh.html" class="function" rel="rdfs-seeAlso">tanh()</a> - Hyperbolic tangent</span></li>
<li class="member"> <span class="function"><a href="function.atan.html" class="function" rel="rdfs-seeAlso">atan()</a> - Arc tangent</span></li>
<li class="member"> <span class="function"><a href="function.asinh.html" class="function" rel="rdfs-seeAlso">asinh()</a> - Inverse hyperbolic sine</span></li>
<li class="member"> <span class="function"><a href="function.acosh.html" class="function" rel="rdfs-seeAlso">acosh()</a> - Inverse hyperbolic cosine</span></li>
</ul>
</p>
</div>
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