---
title: Math.tan()
slug: Web/JavaScript/Reference/Global_Objects/Math/tan
translation_of: Web/JavaScript/Reference/Global_Objects/Math/tan
---
<div>
 {{JSRef("Global_Objects", "Math")}}</div>
<h2 id="Summary" name="Summary">概述</h2>
<p><code><strong>Math.tan()</strong></code> 方法返回一个数值的正切值。</p>
<h2 id="Syntax" name="Syntax">语法</h2>
<pre class="syntaxbox">Math.tan(<em>x</em>)</pre>
<h3 id="Parameters" name="Parameters">参数</h3>
<dl>
 <dt>
  <code>x</code></dt>
 <dd>
  一个数值，表示一个角（单位：弧度）。</dd>
</dl>
<h2 id="Description" name="Description">描述</h2>
<p><code>tan</code> 方法返回一个数值，表示一个角的正切值。</p>
<p>由于 <code>tan</code> 是 <code>Math</code> 的静态方法，所以应该像这样使用 <code>Math.tan()</code>，而不是作为你创建的 <code>Math</code> 实例的方法。</p>
<h2 id="Examples" name="Examples">示例</h2>
<h3 id="Example:_Using_Math.tan" name="Example:_Using_Math.tan">例子：使用 <code>Math.tan</code></h3>
<p>下面的函数返回变量 <code>x</code> 的正切值：</p>
<pre class="brush:js">function getTan(x) {
   return Math.tan(x);
}</pre>
<p>由于 <code>Math.tan()</code> 函数接受弧度数值，但是通常使用度更方便，下面的函数可以接受以度为单位的数值，将其转为弧度，然后返回其正切值。</p>
<pre class="brush:js">function getTanDeg(deg) {
   var rad = deg * Math.PI/180;
   return Math.tan(rad);
}
</pre>
<h2 id="规范">规范</h2>
<table class="standard-table">
 <tbody>
  <tr>
   <th scope="col">规范版本</th>
   <th scope="col">规范状态</th>
   <th scope="col">注解</th>
  </tr>
  <tr>
   <td>ECMAScript 1st Edition. Implemented in JavaScript 1.0</td>
   <td>Standard</td>
   <td>Initial definition.</td>
  </tr>
  <tr>
   <td>{{SpecName('ES5.1', '#sec-15.8.2.18', 'Math.tan')}}</td>
   <td>{{Spec2('ES5.1')}}</td>
   <td> </td>
  </tr>
  <tr>
   <td>{{SpecName('ES6', '#sec-math.tan', 'Math.tan')}}</td>
   <td>{{Spec2('ES6')}}</td>
   <td> </td>
  </tr>
 </tbody>
</table>
<h2 id="浏览器兼容性">浏览器兼容性</h2>
<p>{{ CompatibilityTable() }}</p>
<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>{{ CompatVersionUnknown() }}</td>
    <td>{{ CompatVersionUnknown() }}</td>
    <td>{{ CompatVersionUnknown() }}</td>
    <td>{{ CompatVersionUnknown() }}</td>
    <td>{{ CompatVersionUnknown() }}</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>{{ CompatVersionUnknown() }}</td>
    <td>{{ CompatVersionUnknown() }}</td>
    <td>{{ CompatVersionUnknown() }}</td>
    <td>{{ CompatVersionUnknown() }}</td>
    <td>{{ CompatVersionUnknown() }}</td>
    <td>{{ CompatVersionUnknown() }}</td>
   </tr>
  </tbody>
 </table>
</div>
<p> </p>