# Math.asin()

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The Math.asin() function returns the arcsine (in radians) of a number, that is

$∀x∊[-1;1],Math.asin(x)=arcsin(x)= the unique y∊[-π2;π2]such thatsin(y)=x\forall x \in [{-1};1],\;\mathtt{\operatorname{Math.asin}(x)} = \arcsin(x) = \text{ the unique } \; y \in \left[-\frac{\pi}{2}; \frac{\pi}{2}\right] \, \text{such that} \; \sin(y) = x$

## Syntax

Math.asin(x)

x
A number.

### Return value

The arcsine (in radians) of the given number if it's between -1 and 1; otherwise, NaN.

## Description

The Math.asin() method returns a numeric value between $-\frac\left\{\pi\right\}\left\{2\right\}$ and $\frac\left\{\pi\right\}\left\{2\right\}$ radians for x between -1 and 1. If the value of x is outside this range, it returns NaN.

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


For values less than -1 or greater than 1, Math.asin() returns NaN.

## Specifications

Specification Status Comment
ECMAScript Latest Draft (ECMA-262)
The definition of 'Math.asin' in that specification.
Draft
ECMAScript 2015 (6th Edition, ECMA-262)
The definition of 'Math.asin' in that specification.
Standard
ECMAScript 5.1 (ECMA-262)
The definition of 'Math.asin' in that specification.
Standard
ECMAScript 1st Edition (ECMA-262) Standard Initial definition. Implemented in JavaScript 1.0.

## Browser compatibility

Update compatibility data on GitHub
Desktop Mobile Server Chrome Edge Firefox Internet Explorer Opera Safari Android webview Chrome for Android Firefox for Android Opera for Android Chrome Full support Yes Edge Full support 12 Firefox Full support 1 IE Full support Yes Opera Full support Yes Safari Full support Yes WebView Android Full support Yes Chrome Android Full support Yes Firefox Android Full support 4 Opera Android Full support Yes Safari iOS Full support Yes Samsung Internet Android Full support Yes nodejs Full support Yes

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