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
 *
 * */