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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

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 -π2-\frac{\pi}{2} and π2\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

Browser compatibilityUpdate compatibility data on GitHub

Desktop
Chrome Edge Firefox Internet Explorer Opera Safari
Basic support Yes Yes 1 Yes Yes Yes
Mobile
Android webview Chrome for Android Edge Mobile Firefox for Android Opera for Android iOS Safari Samsung Internet
Basic support Yes Yes Yes 4 Yes Yes Yes
Server
Node.js
Basic support Yes

See also

© 2005–2018 Mozilla Developer Network and individual contributors.
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/atan