What javascript MATH.PI MATH.SQRT really does?
<pre><code>var a=Math.sqrt(0);
var b=Math.sqrt(1);
var c=Math.sqrt(9);
var d=Math.sqrt(64);
var e=Math.sqrt(-9);
</code></pre>

<p>I do not quite understand what does <code>Math.PI</code> and <code>Math.sqrt</code> exactly?</p>
