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

<p><strong><code>Math.cosh()</code></strong> 函数返回数值的双曲余弦函数, 可用 {{jsxref("Math.E", "constant e", "", 1)}} 表示:</p>

<p><math display="block"><semantics><mrow><mstyle mathvariant="monospace"><mo lspace="0em" rspace="thinmathspace">Math.cosh(x)</mo></mstyle><mo>=</mo><mfrac><mrow><msup><mi>e</mi><mi>x</mi></msup><mo>+</mo><msup><mi>e</mi><mrow><mo>-</mo><mi>x</mi></mrow></msup></mrow><mn>2</mn></mfrac></mrow><annotation encoding="TeX">\mathtt{\operatorname{Math.cosh(x)}} = \frac{e^x + e^{-x}}{2}</annotation></semantics></math></p>

<h2 id="Syntax">Syntax</h2>

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

<h3 id="参数">参数</h3>

<dl>
 <dt><code>x</code></dt>
 <dd>数值.</dd>
</dl>

<h2 id="描述">描述</h2>

<p>由于<code>cosh()</code> 是Math的静态函数, 只需通过<code>Math.cosh() </code>调用,而不用通过创建Math对象来调用.</p>

<h2 id="示例">示例</h2>

<h3 id="使用_Math.cosh()">使用 <code>Math.cosh()</code></h3>

<pre class="brush: js">Math.cosh(0);  // 1
Math.cosh(1);  // 1.5430806348152437
Math.cosh(-1); // 1.5430806348152437
</pre>

<h2 id="Polyfill">Polyfill</h2>

<p>可通过 {{jsxref("Math.exp()")}} 函数模拟实现:</p>

<pre class="brush: js">Math.cosh = Math.cosh || function(x) {
  return (Math.exp(x) + Math.exp(-x)) / 2;
}
</pre>

<p>或只调用一次 {{jsxref("Math.exp()")}} 函数:</p>

<pre class="brush: js">Math.cosh = Math.cosh || function(x) {
  var y = Math.exp(x);
  return (y + 1 / y) / 2;
};
</pre>

<h2 id="规范">规范</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('ES6', '#sec-math.cosh', 'Math.cosh')}}</td>
   <td>{{Spec2('ES6')}}</td>
   <td>Initial definition.</td>
  </tr>
 </tbody>
</table>

<h2 id="浏览器兼容性">浏览器兼容性</h2>

{{Compat}}

<h2 id="相关链接">相关链接</h2>

<ul>
 <li>{{jsxref("Math.acosh()")}} {{experimental_inline}}</li>
 <li>{{jsxref("Math.asinh()")}} {{experimental_inline}}</li>
 <li>{{jsxref("Math.atanh()")}} {{experimental_inline}}</li>
 <li>{{jsxref("Math.sinh()")}} {{experimental_inline}}</li>
 <li>{{jsxref("Math.tanh()")}} {{experimental_inline}}</li>
</ul>