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METHOD:  Math::atan2
Math.atan2(y, x)
 
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

 


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