## 概述

`Math.cos()` 函数返回一个数值的余弦值。

## 语法

    Math.cos(x)

### 参数

`x`
  一个以弧度为单位的数值。

## 描述

`cos` 方法返回一个 -1 到 1 之间的数值，表示角度（单位：弧度）的余弦值。

由于 `cos` 是 `Math` 的静态方法，所以应该像这样使用：`Math.cos()`，而不是作为你创建的 `Math` 实例的方法。

## 示例

### 例子：使用 `Math.cos`

    Math.cos(0);           // 1
    Math.cos(1);           // 0.5403023058681398

    Math.cos(Math.PI);     // -1
    Math.cos(2 * Math.PI); // 1

## 规范

规范版本 | 规范状态 | 注解
--- | --- | ---
ECMAScript 1st Edition. Implemented in JavaScript 1.0 | Standard | Initial definition.
ECMAScript 5.1 (ECMA-262) Math.cos | Standard |
ECMAScript 2015 (6th Edition, ECMA-262) Math.cos | Standard |

## 浏览器兼容性

We're converting our compatibility data into a machine-readable JSON format. This compatibility table still uses the old format, because we haven't yet converted the data it contains. Find out how you can help!

- Desktop
- Mobile

Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari
--- | --- | --- | --- | --- | ---
Basic support | (Yes) | (Yes) | (Yes) | (Yes) | (Yes)

Feature | Android | Chrome for Android | Firefox Mobile (Gecko) | IE Mobile | Opera Mobile | Safari Mobile
--- | --- | --- | --- | --- | --- | ---
Basic support | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) | (Yes)

## 相关链接

- The `Math` object it belongs to.