---
title: atan2d
description: "计算y/x的反正切的角度值。"
url: https://www.hikunpeng.com/document/detail/zh/kunpenghpcs/hpckit/devg/kunpengaccel_kml_0167.html
sourcePath: /source/zh/kunpenghpcs/hpckit/devg/kunpengaccel_kml_0167.html
indexId: 40087e0bb349db8b665864616be5ac0cffe4f1762bbab4cc0f3b51032c644bc761
---
# atan2d

计算y/x的反正切的角度值。

#### 接口定义

C interface：

float atan2df(float y, float x);

double atan2d(double y, double x);

long double atan2dl(long double y, long double x);


#### 参数

| 参数名 | 类型 | 描述 | 输入/输出 |
| --- | --- | --- | --- |
| x | 在atan2df中，x是单精度浮点类型。 在atan2d中，x是双精度浮点类型。 在atan2dl中，x是长双精度浮点类型。 | 表示输入数据的浮点值。 | 输入 |
| y | 在atan2df中，y是单精度浮点类型。 在atan2d中，y是双精度浮点类型。 在atan2dl中，y是长双精度浮点类型。 | 表示输入数据的浮点值。 | 输入 |


#### 返回值

- 正常区间：返回y/x的反正切的角度值，即atan2d(y, x) = atan2(y, x) * 180 / π。
- 特殊区间：如下所示。| 输入值（y） | 输入值（x） | 输出值（result） |
| --- | --- | --- |
| +0 | +0 | +0 |
| +0 | \-0 | 180 |
| +0 | inf | +0 |
| +0 | \-inf | 180 |
| +0 | nan | nan |
| \-0 | +0 | \-0 |
| \-0 | \-0 | \-180 |
| \-0 | inf | \-0 |
| \-0 | \-inf | \-180 |
| \-0 | nan | nan |
| inf | +0 | 90 |
| inf | \-0 | 90 |
| inf | inf | 45 |
| inf | \-inf | 135 |
| inf | nan | nan |
| \-inf | +0 | \-90 |
| \-inf | \-0 | \-90 |
| \-inf | inf | \-45 |
| \-inf | \-inf | \-135 |
| \-inf | nan | nan |
| nan | +0 | nan |
| nan | \-0 | nan |
| nan | inf | nan |
| nan | \-inf | nan |
| nan | nan | nan |


#### 依赖

C: "km.h"


#### 示例

C interface：```
// typical usage
float x1 = -1.0, x2 = 1.0, x3 = 0.5, x4 = -0.5;
// special handling
float a = 0.0, b = INFINITY, c = -INFINITY, d = NAN;
// print result
printf("atan2d(1.0, 1.0) = %.15f\n", atan2d(x1, x1));
printf("atan2d(-1.0, -1.0) = %.15f\n", atan2d(x2, x2));
printf("atan2d(0.5, 0.5) = %.15f\n", atan2d(x3, x3));
printf("atan2d(-0.5, -0.5) = %.15f\n", atan2d(x4, x4));
printf("atan2d(0.0, 0.0) = %.15f\n", atan2d(a, a));
printf("atan2d(-0.0, -0.0) = %.15f\n", atan2d(-a, -a));
printf("atan2d(INFINITY, INFINITY) = %.15f\n", atan2d(b, b));
printf("atan2d(-INFINITY, -INFINITY) = %.15f\n", atan2d(c, c));
printf("atan2d(NAN, NAN) = %.15f\n", atan2d(d, d));
/*
 *  atan2d(1.0, 1.0) = -135.000000000000000
 *  atan2d(-1.0, -1.0) = 45.000000000000000
 *  atan2d(0.5, 0.5) = 45.000000000000000
 *  atan2d(-0.5, -0.5) = -135.000000000000000
 *  atan2d(0.0, 0.0) = 0.000000000000000
 *  atan2d(-0.0, -0.0) = -180.000000000000000
 *  atan2d(INFINITY, INFINITY) = 45.000000000000000
 *  atan2d(-INFINITY, -INFINITY) = -135.000000000000000
 *  atan2d(NAN, NAN) = nan
 *
 * */
```