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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




A number.

Return value

The arctangent (in radians) of the given number.


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).


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.


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

Browser compatibility

Update compatibility data on GitHub
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung InternetNode.js
atanChrome Full support 1Edge Full support 12Firefox Full support 1IE Full support 3Opera Full support YesSafari Full support YesWebView Android Full support 1Chrome Android Full support 18Firefox Android Full support 4Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support 1.0nodejs Full support Yes


Full support  
Full support

See also