# Math.acos()

Math.acos() 함수는 주어진 수의 아크코사인 값을 숫자(라디안)로 반환합니다. 즉,

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

## 구문

Math.acos(x)

### 매개변수

x
각도를 나타내는 라디안.

### 반환 값

-1과 1 사이의 값이 주어진 경우, 그 값의 아크코사인. 아닐 경우 NaN

## 설명

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).

## 예제

### 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.

## 명세

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

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