<h3>atan() function</h3>
Returns arcustanget of a value in radians.


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

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

<p><h4>Example</h4>
     atan(0.5) &rarr; 0.463647609000806</p>
