## 概述

`Math.atan()` 函数返回一个数值的反正切（以弧度为单位），即：

Math.atan(x)=arctan(x)= the unique y∊[-π 2;π 2]such that tan(y)=x\mathtt{\operatorname{Math.atan}(x)} = \arctan(x) = \text{ the unique } \; y \in \left[-\frac{\pi}{2}; \frac{\pi}{2}\right] \, \text{such that} \; \tan(y) = x

## 语法

    Math.atan(x)

### 参数

`x`
  一个数值

## 描述

`atan` 返回一个 -π 2-\frac{\pi}{2} 到 π 2\frac{\pi}{2} 弧度之间的数值。

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

## 示例

### 例子：使用 `Math.atan`

    Math.atan(1);  // 0.7853981633974483
    Math.atan(0);  // 0

## 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.atan | Standard |
ECMAScript 2015 (6th Edition, ECMA-262) Math.atan | 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.
- `Math.acos()`
- `Math.asin()`
- `Math.atan2()`
- `Math.cos()`
- `Math.sin()`
- `Math.tan()`