Math.asin()

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.asin() static method returns the inverse sine (in radians) of a number. That is,

\forall x \in [{-1}, 1],\;\mathtt{\operatorname{Math.asin}(x)} = \arcsin(x) = \text{the unique } y \in \left[-\frac{\pi}{2}, \frac{\pi}{2}\right] \text{ such that } \sin(y) = x

Try it

// Calculates angle of a right-angle triangle in radians
function calcAngle(opposite, hypotenuse) {
  return Math.asin(opposite / hypotenuse);
}

console.log(calcAngle(6, 10));
// Expected output: 0.6435011087932844

console.log(calcAngle(5, 3));
// Expected output: NaN

Syntax

Math.asin(x)

Parameters

x: A number between -1 and 1, inclusive, representing the angle's sine value.

Return value

The inverse sine (angle in radians between $-\frac{\pi}{2}$ and $\frac{\pi}{2}$ , inclusive) of x. If x is less than -1 or greater than 1, returns NaN.

Description

Because asin() is a static method of Math, you always use it as Math.asin(), rather than as a method of a Math object you created (Math is not a constructor).

Examples

Using Math.asin()

Math.asin(-2); // NaN
Math.asin(-1); // -1.5707963267948966 (-π/2)
Math.asin(-0); // -0
Math.asin(0); // 0
Math.asin(0.5); // 0.5235987755982989 (π/6)
Math.asin(1); // 1.5707963267948966 (π/2)
Math.asin(2); // NaN

Specifications

Specification
ECMAScript® 2026 Language Specification # sec-math.asin

Browser compatibility

	Desktop					Mobile						Server
	Chrome	Edge	Firefox	Opera	Safari	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet	WebView Android	Deno	Node.js
`asin`	1	12	1	3	1	18	4	10.1	1	1.0	4.4	1.0	0.10.0