Can someone show me how to properly write Math.cos or Math.acos for android
<p>I have tried writing this in android and I get NAN as the result. 
this is my current code can someone verify this correct and if not offer me the correct equation. Thank you.</p>

<pre><code> Math.acos((((a*a)+(c*c))-(b*b))/(2*b*c));
</code></pre>

<p><img src="http://i.stack.imgur.com/L6bPJ.jpg" alt="enter image description here"></p>
