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---
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>
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