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    Math.acos()

    Summary

    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 thatcos(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

    Syntax

    Math.acos(x)

    Parameters

    x
    A number.

    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

    Example: 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

    Specification Status Comment
    ECMAScript 1st Edition. Standard Initial definition. Implemented in JavaScript 1.0.
    ECMAScript 5.1 (ECMA-262)
    The definition of 'Math.acos' in that specification.
    Standard  
    ECMAScript 6 (ECMA-262)
    The definition of 'Math.acos' in that specification.
    Release Candidate  

    Browser compatibility

    Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari
    Basic support (Yes) (Yes) (Yes) (Yes) (Yes)
    Feature Android Chrome for Android Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
    Basic support (Yes) (Yes) (Yes) (Yes) (Yes) (Yes)

    See also

    Document Tags and Contributors

    Last updated by: Mingun,