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.

The Math.atan() static method returns the inverse tangent (in radians) of a number, that is

𝙼𝚊𝚝𝚑.𝚊𝚝𝚊𝚗(𝚡)=arctan(x)=the unique y[π2,π2] such that tan(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

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Syntax

js
Math.atan(x)

Parameters

x

A number.

Return value

The inverse tangent (angle in radians between -π2-\frac{\pi}{2} and π2\frac{\pi}{2}, inclusive) of x. If x is Infinity, it returns π2\frac{\pi}{2}. If x is -Infinity, it returns -π2-\frac{\pi}{2}.

Description

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()

js
Math.atan(-Infinity); // -1.5707963267948966 (-π/2)
Math.atan(-0); // -0
Math.atan(0); // 0
Math.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 system
const theta = (x, y) => Math.atan(y / x);

Note that you may want to avoid the theta function and use Math.atan2() instead, which has a wider range (between -π and π) and avoids outputting NaN for cases such as when x is 0.

Specifications

Specification
ECMAScript Language Specification
# sec-math.atan

Browser compatibility

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See also