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---
title: Math.atanh()
slug: Web/JavaScript/Reference/Global_Objects/Math/atanh
translation_of: Web/JavaScript/Reference/Global_Objects/Math/atanh
---
<div>{{JSRef}}</div>
<p><strong><code>Math.atanh()</code></strong> 函数返回一个数值反双曲正切值, 即：</p>
<p><math display="block"><semantics><mrow><mo>∀</mo><mi>x</mi><mo>∊</mo><mrow><mo>(</mo><mrow><mo>-</mo><mn>1</mn><mo>,</mo><mn>1</mn></mrow><mo>)</mo></mrow><mo>,</mo><mstyle mathvariant="monospace"><mrow><mo lspace="0em" rspace="thinmathspace">Math.atanh</mo><mo stretchy="false">(</mo><mi>x</mi><mo stretchy="false">)</mo></mrow></mstyle><mo>=</mo><mo lspace="0em" rspace="thinmathspace">arctanh</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><mspace width="thickmathspace"></mspace><mtext>such that</mtext><mspace width="thickmathspace"></mspace><mo lspace="0em" rspace="0em">tanh</mo><mo stretchy="false">(</mo><mi>y</mi><mo stretchy="false">)</mo><mo>=</mo><mi>x</mi></mrow><annotation encoding="TeX">\forall x \in \left( -1, 1 \right), \mathtt{\operatorname{Math.atanh}(x)} = \operatorname{arctanh}(x) = \text{ the unique } \; y \; \text{such that} \; \tanh(y) = x</annotation></semantics></math></p>
<h2 id="语法">语法</h2>
<pre class="syntaxbox"><code>Math.atanh(<var>x</var>)</code></pre>
<h3 id="参数">参数</h3>
<dl>
<dt><code>x</code></dt>
<dd>一个数值</dd>
</dl>
<h2 id="描述">描述</h2>
<p>由于 <code>atanh()</code> 是 <code>Math 的静态方法</code>,所以应该像这样使用：<code>Math.atanh()</code>，而不是作为你创建的 <code>Math</code> 实例的方法（<code>Math 不是一个构造函数</code>）。 </p>
<h2 id="示例">示例</h2>
<h3 id="使用_Math.atanh()"><code>使用 Math.atanh()</code></h3>
<pre class="brush: js">Math.atanh(-2); // NaN
Math.atanh(-1); // -Infinity
Math.atanh(0); // 0
Math.atanh(0.5); // 0.5493061443340548
Math.atanh(1); // Infinity
Math.atanh(2); // NaN
</pre>
<p>对于大于1或是小于－1的值，函数返回 {{jsxref("NaN")}} 。</p>
<h2 id="Polyfill">Polyfill</h2>
<p>For \left|x\right| < 1, we have \operatorname {artanh} (x) = \frac{1}{2}\ln \left( \frac{1 + x}{1 - x} \right) so this can be emulated by the following function:</p>
<pre class="brush: js">Math.atanh = Math.atanh || function(x) {
return Math.log((1+x)/(1-x)) / 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.atanh', 'Math.atanh')}}</td>
<td>{{Spec2('ES6')}}</td>
<td>Initial definition.</td>
</tr>
<tr>
<td>{{SpecName('ESDraft', '#sec-math.atanh', 'Math.atanh')}}</td>
<td>{{Spec2('ESDraft')}}</td>
<td> </td>
</tr>
</tbody>
</table>
<h2 id="浏览器兼容性">浏览器兼容性</h2>
<div>{{CompatibilityTable}}</div>
<div id="compat-desktop">
<table class="compat-table">
<tbody>
<tr>
<th>Feature</th>
<th>Chrome</th>
<th>Firefox (Gecko)</th>
<th>Internet Explorer</th>
<th>Opera</th>
<th>Safari</th>
</tr>
<tr>
<td>Basic support</td>
<td>{{CompatChrome("38")}}</td>
<td>{{CompatGeckoDesktop("25")}}</td>
<td>{{CompatNo}}</td>
<td>{{CompatOpera("25")}}</td>
<td>{{CompatSafari("7.1")}}</td>
</tr>
</tbody>
</table>
</div>
<div id="compat-mobile">
<table class="compat-table">
<tbody>
<tr>
<th>Feature</th>
<th>Android</th>
<th>Chrome for Android</th>
<th>Firefox Mobile (Gecko)</th>
<th>IE Mobile</th>
<th>Opera Mobile</th>
<th>Safari Mobile</th>
</tr>
<tr>
<td>Basic support</td>
<td>{{CompatNo}}</td>
<td>{{CompatNo}}</td>
<td>{{CompatGeckoMobile("25")}}</td>
<td>{{CompatNo}}</td>
<td>{{CompatNo}}</td>
<td>8</td>
</tr>
</tbody>
</table>
</div>
<h2 id="相关链接">相关链接</h2>
<ul>
<li>{{jsxref("Math.acosh()")}}</li>
<li>{{jsxref("Math.asinh()")}}</li>
<li>{{jsxref("Math.cosh()")}}</li>
<li>{{jsxref("Math.sinh()")}}</li>
<li>{{jsxref("Math.tanh()")}}</li>
</ul>
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