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Math.acos()

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

x [ - 1 ; 1 ] , Math.acos ( x ) = arccos ( x ) = the unique y [ 0 ; π ] such that cos ( y ) = x \forall x \in [{-1};1],;\mathtt{\operatorname{Math.acos}(x)} = \arccos(x) = \text{ the unique } ; y \in [0; \pi] , \text{such that} ; \cos(y) = x

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Syntax

Math.acos(x)

Parameters

x

A number representing a cosine, where x is between -1 and 1.

Return value

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

Description

The Math.acos() method returns a numeric value between 0 and π radians for x between -1 and 1. If the value of x is outside this range, it returns NaN.

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

Examples

Using Math.acos()

Math.acos(-2);  // NaN
Math.acos(-1);  // 3.141592653589793
Math.acos(0);   // 1.5707963267948966
Math.acos(0.5); // 1.0471975511965979
Math.acos(1);   // 0
Math.acos(2);   // NaN

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

Specifications

Browser compatibility

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

See also

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Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/acos