<h3>acos() function</h3>
Returns arcuscosinus of a value in radians.


<p><h4>Syntax</h4>
     acos(<i>real</i>)</p>

<p><h4>Arguments</h4>
<i>real</i> &rarr; cos of an angle.</p>

<p><h4>Example</h4>
     acos(0.5) &rarr; 1.0471975511966</p>
