===== Cosine ======

==== cos( a ) ====

Return the cosine of a.

=== Description ===

<code>cos( a )</code>

Return the cosine of a, where a is the angle in radians.

=== Parameters ===

| ''a'' | Angle in radians |

=== Return value ===

cosine of a

=== Example usage ===

<code>cos( PI/2 )</code>

Returns 0.