Math.atan2()

The Math.atan2() function returns the angle in the plane (in radians) between the positive x-axis and the ray from (0, 0) to the point (x, y), for Math.atan2(y, x).

Syntax

Math.atan2(y, x)

Parameters

• y
  • : The y coordinate of the point.
• x
  • : The x coordinate of the point.

Return value

The angle in radians (between -π and π, inclusive) between the positive x-axis and the ray from (0, 0) to the point (x, y).

Description

The Math.atan2() method measures the counterclockwise angle θ, in radians, between the positive x-axis and the point (x, y). Note that the arguments to this function pass the y-coordinate first and the x-coordinate second.

Math.atan2() is passed separate x and y arguments, while Math.atan() is passed the ratio of those two arguments. Math.atan2(y, x) differs from Math.atan(y / x) in the following cases:

x	y	Math.atan2(y, x)	Math.atan(y / x)
Infinity	Infinity	π / 4	NaN
Infinity	-Infinity	-π / 4	NaN
-Infinity	Infinity	3π / 4	NaN
-Infinity	-Infinity	-3π / 4	NaN
0	0	0	NaN
0	-0	-0	NaN
< 0 (including -0)	0	π	0
< 0 (including -0)	-0	-π	0
-Infinity	> 0	π	-0
-0	> 0	π / 2	-π / 2
-Infinity	< 0	-π	0
-0	< 0	-π / 2	π / 2

In addition, for points in the second and third quadrants (x < 0), Math.atan2() would output an angle less than $-\frac{\pi}{2}$ or greater than $\frac{\pi}{2}$.

Because atan2() is a static method of Math, you always use it as Math.atan2(), rather than as a method of a Math object you created (Math is not a constructor).