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

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support Yes Yes1 Yes Yes Yes
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support Yes Yes Yes4 Yes Yes Yes

See also

Document Tags and Contributors

Last updated by: wbamberg,