Math.atan()
Baseline Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.
TheMath.atan() static method returns the inverse tangent (in radians) of a number, that is
Try it
// Calculates angle of a right-angle triangle in radiansfunction calcAngle(opposite, adjacent) { return Math.atan(opposite / adjacent);}console.log(calcAngle(8, 10));// Expected output: 0.6747409422235527console.log(calcAngle(5, 3));// Expected output: 1.0303768265243125Syntax
js
Math.atan(x)Parameters
xA number.
Return value
The inverse tangent (angle in radians between and, inclusive) ofx. Ifx isInfinity, it returns. Ifx is-Infinity, it returns.
Description
Becauseatan() is a static method ofMath, you always use it asMath.atan(), rather than as a method of aMath object you created (Math is not a constructor).
Examples
Using Math.atan()
js
Math.atan(-Infinity); // -1.5707963267948966 (-π/2)Math.atan(-0); // -0Math.atan(0); // 0Math.atan(1); // 0.7853981633974483 (π/4)Math.atan(Infinity); // 1.5707963267948966 (π/2)// The angle that the line (0,0) -- (x,y) forms with the x-axis in a Cartesian coordinate systemconst theta = (x, y) => Math.atan(y / x);Note that you may want to avoid thetheta function and useMath.atan2() instead, which has a wider range (between -π and π) and avoids outputtingNaN for cases such as whenx is0.
Specifications
| Specification |
|---|
| ECMAScript® 2026 Language Specification # sec-math.atan |