---
title: Math.acos()
slug: Web/JavaScript/Reference/Global_Objects/Math/acos
tags:
  - JavaScript
  - Math
  - Method
  - Reference
translation_of: Web/JavaScript/Reference/Global_Objects/Math/acos
---
<div>{{JSRef}}</div>

<p><strong><code>Math.acos()</code></strong> 함수는 주어진 수의 아크코사인 값을 숫자(라디안)로 반환합니다. 즉,</p>

<p><math display="block"><semantics><mrow><mo>∀</mo><mi>x</mi><mo>∊</mo><mo stretchy="false">[</mo><mrow><mo>-</mo><mn>1</mn></mrow><mo>;</mo><mn>1</mn><mo stretchy="false">]</mo><mo>,</mo><mspace width="thickmathspace"></mspace><mstyle mathvariant="monospace"><mrow><mo lspace="0em" rspace="thinmathspace">Math.acos</mo><mo stretchy="false">(</mo><mi>x</mi><mo stretchy="false">)</mo></mrow></mstyle><mo>=</mo><mo lspace="0em" rspace="0em">arccos</mo><mo stretchy="false">(</mo><mi>x</mi><mo stretchy="false">)</mo><mo>=</mo><mtext> the unique </mtext><mspace width="thickmathspace"></mspace><mi>y</mi><mo>∊</mo><mo stretchy="false">[</mo><mn>0</mn><mo>;</mo><mi>π</mi><mo stretchy="false">]</mo><mspace width="thinmathspace"></mspace><mtext>such that</mtext><mspace width="thickmathspace"></mspace><mo lspace="0em" rspace="0em">cos</mo><mo stretchy="false">(</mo><mi>y</mi><mo stretchy="false">)</mo><mo>=</mo><mi>x</mi></mrow><annotation encoding="TeX">\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</annotation></semantics></math></p>

<div>{{EmbedInteractiveExample("pages/js/math-acos.html")}}</div>



<h2 id="구문">구문</h2>

<pre class="syntaxbox"><code>Math.acos(<var>x</var>)</code></pre>

<h3 id="매개변수">매개변수</h3>

<dl>
 <dt><code>x</code></dt>
 <dd>각도를 나타내는 라디안.</dd>
</dl>

<h3 id="반환_값">반환 값</h3>

<p>-1과 1 사이의 값이 주어진 경우, 그 값의 아크코사인. 아닐 경우 {{jsxref("NaN")}}</p>

<h2 id="설명">설명</h2>

<p>The <code>Math.acos()</code> method returns a numeric value between 0 and π radians for <code>x</code> between -1 and 1. If the value of <code>x</code> is outside this range, it returns {{jsxref("NaN")}}.</p>

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

<h2 id="예제">예제</h2>

<h3 id="Using_Math.acos()">Using <code>Math.acos()</code></h3>

<pre class="brush: js">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
</pre>

<p>For values less than -1 or greater than 1, <code>Math.acos()</code> returns {{jsxref("NaN")}}.</p>

<h2 id="명세">명세</h2>

<table class="standard-table">
 <tbody>
  <tr>
   <th scope="col">Specification</th>
   <th scope="col">Status</th>
   <th scope="col">Comment</th>
  </tr>
  <tr>
   <td>{{SpecName('ES1')}}</td>
   <td>{{Spec2('ES1')}}</td>
   <td>Initial definition. Implemented in JavaScript 1.0.</td>
  </tr>
  <tr>
   <td>{{SpecName('ES5.1', '#sec-15.8.2.2', 'Math.acos')}}</td>
   <td>{{Spec2('ES5.1')}}</td>
   <td> </td>
  </tr>
  <tr>
   <td>{{SpecName('ES6', '#sec-math.acos', 'Math.acos')}}</td>
   <td>{{Spec2('ES6')}}</td>
   <td> </td>
  </tr>
  <tr>
   <td>{{SpecName('ESDraft', '#sec-math.acos', 'Math.acos')}}</td>
   <td>{{Spec2('ESDraft')}}</td>
   <td> </td>
  </tr>
 </tbody>
</table>

<h2 id="브라우저_호환성">브라우저 호환성</h2>



<p>{{Compat("javascript.builtins.Math.acos")}}</p>

<h2 id="See_also">See also</h2>

<ul>
 <li>{{jsxref("Math.asin()")}}</li>
 <li>{{jsxref("Math.atan()")}}</li>
 <li>{{jsxref("Math.atan2()")}}</li>
 <li>{{jsxref("Math.cos()")}}</li>
 <li>{{jsxref("Math.sin()")}}</li>
 <li>{{jsxref("Math.tan()")}}</li>
</ul>