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.

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

\forall x ∊ [- 1, 1], 𝙼𝚊𝚝𝚑.𝚊𝚜𝚒𝚗 (𝚡) = arcsin (x) = the unique y ∊ [- \frac{π}{2}, \frac{π}{2}] 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 radiansfunction calcAngle(opposite, hypotenuse) {  return Math.asin(opposite / hypotenuse);}console.log(calcAngle(6, 10));// Expected output: 0.6435011087932844console.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 $- \frac{π}{2} -\frac{\pi}{2}$ and $\frac{π}{2} \frac{\pi}{2}$ , inclusive) ofx. Ifx is less than -1 or greater than 1, returnsNaN.

Description

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

Examples

Using Math.asin()

Math.asin(-2); // NaNMath.asin(-1); // -1.5707963267948966 (-π/2)Math.asin(-0); // -0Math.asin(0); // 0Math.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

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This page was last modified on⁨Jul 10, 2025⁩ byMDN contributors.

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