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<h3 class="section">1.3 <code>acos</code>, <code>acosf</code>&mdash;arc cosine</h3>

<p><a name="index-acos-1"></a><a name="index-acosf-2"></a><strong>Synopsis</strong>
<pre class="example">     #include &lt;math.h&gt;
     double acos(double <var>x</var>);
     float acosf(float <var>x</var>);
     
</pre>
   <p><strong>Description</strong><br>

   <p><code>acos</code> computes the inverse cosine (arc cosine) of the input value. 
Arguments to <code>acos</code> must be in the range &minus;1 to 1.

   <p><code>acosf</code> is identical to <code>acos</code>, except that it performs
its calculations on <code>floats</code>.

   <pre class="sp">

</pre>
<strong>Returns</strong><br>
<code>acos</code> and <code>acosf</code> return values in radians, in the range of 0 to pi.

   <p>If <var>x</var> is not between &minus;1 and 1, the returned value is NaN
(not a number), and the global variable <code>errno</code> is set to <code>EDOM</code>.

   <pre class="sp">

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