# Math.atan()

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

$Math.atan(x)=arctan(x)= the unique y∊[-π2;π2]such thattan(y)=x\mathtt{\operatorname{Math.atan}(x)} = \arctan(x) = \text{ the unique } \; y \in \left[-\frac{\pi}{2}; \frac{\pi}{2}\right] \, \text{such that} \; \tan(y) = x$

## Syntax

JavaScript
Math.atan(<var>x</var>)

### Parameters

x
A number.

### Return value

The arctangent (in radians) of the given number.

## Description

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

JavaScript
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

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari
Basic support (Yes) (Yes) (Yes) (Yes) (Yes)
Feature Android Chrome for Android Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support (Yes) (Yes) (Yes) (Yes) (Yes) (Yes)