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JavaScript atan() and atan2() Methods

JavaScript Math Object

Definition and Usage

The atan() method returns the arctangent of a number as a numeric value between -PI/2 and PI/2 radians.

The atan2() method returns the arctangent of the quotient of its arguments. 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: With atan2(), the y coordinate is passed as the first argument and the x coordinate is passed as the second argument!

Syntax

Math.atan(x)

Math.atan2(y,x)

Parameter	Description
x	Required. A number
y	Required. A number

Browser Support

The atan() and atan2() methods are supported in all major browsers.

Examples

Example 1 - atan2(y,x)

Assume you had a point with the (x,y) coordinates of (4,8), you could calculate the angle in radians between that point and the positive X axis as follows:

The output of the code above will be:

1.1071487177940904

Try it yourself »

Example 2 - atan(x)

We can also calculate the arctangent of the ratio of the two coordinates above (8/4 = 2), which will produce the same output: