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,

x[1,1],𝙼𝚊𝚝𝚑.𝚊𝚜𝚒𝚗(𝚡)=arcsin(x)=the unique y[π2,π2] such that sin(y)=x\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

js
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 -π2-\frac{\pi}{2} and π2\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()

js
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® 2025 Language Specification
# sec-math.asin

Browser compatibility

Report problems with this compatibility data on GitHub
desktopmobileserver
Chrome
Edge
Firefox
Opera
Safari
Chrome Android
Firefox for Android
Opera Android
Safari on iOS
Samsung Internet
WebView Android
WebView on iOS
Deno
Node.js
asin

Legend

Tip: you can click/tap on a cell for more information.

Full support
Full support

See also