`Math.cosh()` 函数返回数值的双曲余弦函数, 可用 constant e 表示:

Math.cosh(x)=e x+e-x 2\mathtt{\operatorname{Math.cosh(x)}} = \frac{e^x + e^{-x}}{2}

## Syntax

    Math.cosh(x)

### 参数

`x`
  数值.

## 描述

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

## 示例

### 使用 `Math.cosh()`

    Math.cosh(0);  // 1
    Math.cosh(1);  // 1.5430806348152437
    Math.cosh(-1); // 1.5430806348152437

## Polyfill

可通过 `Math.exp()` 函数模拟实现:

    Math.cosh = Math.cosh || function(x) {
      return (Math.exp(x) + Math.exp(-x)) / 2;
    }

或只调用一次 `Math.exp()` 函数:

    Math.cosh = Math.cosh || function(x) {
      var y = Math.exp(x);
      return (y + 1 / y) / 2;
    };

## 规范

Specification | Status | Comment
--- | --- | ---
ECMAScript 2015 (6th Edition, ECMA-262) Math.cosh | Standard | Initial definition.

## 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 | 38 | 25 (25) | 未实现 | 25 | 7.1

Feature | Android | Chrome for Android | Firefox Mobile (Gecko) | IE Mobile | Opera Mobile | Safari Mobile
--- | --- | --- | --- | --- | --- | ---
Basic support | 未实现 | 未实现 | 25.0 (25) | 未实现 | 未实现 | 8

## 相关链接

- `Math.acosh()`
- `Math.asinh()`
- `Math.atanh()`
- `Math.sinh()`
- `Math.tanh()`