Math.atan2( ) 
compute the angle from the Xaxis to a
point 
Availability
JavaScript 1.0; JScript 1.0; ECMAScript v1
Synopsis
Math.atan2(y, x)
Arguments
 y

The Ycoordinate of the point.
 x

The Xcoordinate of the point.
Returns
A value between  and radians that specifies the
counterclockwise angle between the positive Xaxis and the point
(x, y).
Description
The Math.atan2( ) function computes the arc
tangent of the ratio
y/x. The
y argument can be considered the
Ycoordinate (or "rise") of a point, and the
x argument can be considered the
Xcoordinate (or "run") of the point. Note the unusual
order of the arguments to this function: the Ycoordinate is passed
before the Xcoordinate.
