Function atan2( y, x )

Description:
Converts rectangular coordinates (x,y) to polar (r,theta). This method computes the phase theta by computing an arc tangent of y/x in the range of -pi to pi.
Parameters:
y (floating point)
the ordinate coordinate
x (floating point)
the abscissa coordinate
Return Value (floating point):
the theta component (radians) of the point (r,theta) in polar coordinates that corresponds to the point (x,y) in Cartesian coordinates.
Signature:
double atan2(double, double)