The atan2 method returns the arctangent of the quotient of its two arguments. Compare this to the atan method whose single argument is the ratio of these two co-ordinates. Specifically, the angle returned is a numeric value between PI and -PI and represents the counterclockwise angle in radians (not degrees) between the positive X axis and the point (x, y).

NOTE:

The y co-ordinate is passed as the first argument and the x co-ordinate is passed as the second argument, i.e. atan2(y, x). This is purposeful and is agreement with the ECMA-262 standard.

Assuming you had a point with the (x, y) co-ordinates of (3, 6), you could calculate the angle in radians between that point and the positive X axis as follows:

Code:
Math.atan2(6, 3)

output:
0.4636476090008061

This is equivalent to calculating the arctangent of the ratio of these two co-ordinates, which is 6/3 = 2, as follows:

Code:
Math.atan(2)

output:
0.4636476090008061

Copyright 1999 by Infinite Software Solutions, Inc.
Trademark Information