Math.atan

The Math.atan() function returns the arctangent (in radians) of a number, that is

$$\mathtt{\operatorname{Math.atan}(x)} = \arctan(x) = \text{ the unique } \; y \in \left[-\frac{\pi}{2}; \frac{\pi}{2}\right] \, \text{such that} \; \tan(y) = x$$

Syntax

Math.atan(x)

Parameters

x

A number.

Return value

The arctangent (in radians) of the given number.

Description

The Math.atan() method returns a numeric value between $-\frac{\pi}{2}$ and $\frac{\pi}{2}$ radians.

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

Examples

Using Math.atan()

Math.atan(1);   // 0.7853981633974483
Math.atan(0);   // 0
Math.atan(-0);  // -0

Math.atan(Infinity);   //  1.5707963267948966
Math.atan(-Infinity);  // -1.5707963267948966

// The angle that the line [(0,0);(x,y)] forms with the x-axis in a Cartesian coordinate system
Math.atan(y / x);

Note that you may want to avoid using ±Infinity for stylistic reasons. In this case, Math.atan2() with 0 as the second argument may be a better solution.

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.atan' in that specification.	Standard
ECMAScript 2015 (6th Edition, ECMA-262) The definition of 'Math.atan' in that specification.	Standard
ECMAScript 2017 Draft (ECMA-262) The definition of 'Math.atan' in that specification.	Draft

Browser compatibility

See also

• Math.acos()
• Math.asin()
• Math.atan2()
• Math.cos()
• Math.sin()
• Math.tan()