Math.atan2

The Math.atan2() function returns the arctangent of the quotient of its arguments.

Syntax

Math.atan2(y, x)

Parameters

y

First number.

x

Second number.

Return value

The arctangent of the quotient of the given arguments.

Description

The Math.atan2() method returns a numeric value between -π and π representing the angle theta of an (x, y) point. This is the counterclockwise angle, measured 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, and Math.atan() is passed the ratio of those two arguments.

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).

Examples

Using Math.atan2()

Math.atan2(90, 15); // 1.4056476493802699
Math.atan2(15, 90); // 0.16514867741462683

Math.atan2(±0, -0);               // ±PI.
Math.atan2(±0, +0);               // ±0.
Math.atan2(±0, -x);               // ±PI for x > 0.
Math.atan2(±0, x);                // ±0 for x > 0.
Math.atan2(-y, ±0);               // -PI/2 for y > 0.
Math.atan2(y, ±0);                // PI/2 for y > 0.
Math.atan2(±y, -Infinity);        // ±PI for finite y > 0.
Math.atan2(±y, +Infinity);        // ±0 for finite y > 0.
Math.atan2(±Infinity, x);         // ±PI/2 for finite x.
Math.atan2(±Infinity, -Infinity); // ±3*PI/4.
Math.atan2(±Infinity, +Infinity); // ±PI/4.

Specifications

Specification	Status	Comment
ECMAScript 1st Edition (ECMA-262)	Standard	Initial definition. Implemented in JavaScript 1.0.
ECMAScript 5.1 (ECMA-262) The definition of 'Math.atan2' in that specification.	Standard
ECMAScript 2015 (6th Edition, ECMA-262) The definition of 'Math.atan2' in that specification.	Standard
ECMAScript 2017 Draft (ECMA-262) The definition of 'Math.atan2' in that specification.	Draft

Browser compatibility

See also

• Math.acos()
• Math.asin()
• Math.atan()
• Math.cos()
• Math.sin()
• Math.tan()