(PHP 3 >= 3.0.5, PHP 4, PHP 5)
atan2 -- Arc tangent of two variables
( float y, float x )
This function calculates the arc tangent of the two variables
x and y. It is
similar to calculating the arc tangent of
y / x, except that
the signs of both arguments are used to determine the quadrant of
The function returns the result in radians, which is between -PI
and PI (inclusive).
See also acos() and atan().