EFUN: acos

SYNTAX:
float acos( x );
  float x;

DESCRIPTION:
Calculates the arccosine of x. X must be a value between -1 and 1.

RETURN VALUE:
The value of acos( x ) is returned (varies between 0 and PI).

SEE ALSO:
cos
asin
atan

EXAMPLE:
float x;

x = acos( 1.0 );
// x has now a value of 0.
