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)

Parameters

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 -π2-\frac{\pi}{2} and π2\frac{\pi}{2} 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
DesktopMobileServer
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung InternetNode.js
asinChrome Full support 1Edge Full support 12Firefox Full support 1IE Full support 3Opera Full support YesSafari Full support YesWebView Android Full support 1Chrome Android Full support 18Firefox Android Full support 4Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support 1.0nodejs Full support Yes

Legend

Full support  
Full support

See also