atan2(y, x)函数用法详解

代码示例：

 1 #include 
 2 #define M_PI       3.14159265358979323846   // pi
 3 
 4 using namespace std;
 5 
 6 int main()
 7 {
 8     double x = 100;
 9     double y = 1;
10     double abs1, abs2, abs3, abs4;
11     abs1 = atan2(y, x) * 180 / M_PI;
12     cout << "第一象限角abs1= " << abs1 << endl;
13     abs2 = atan2(y, -x) * 180 / M_PI;
14     cout << "第二象限角abs2= " << abs2 << endl;
15     abs3 = atan2(-y, -x) * 180 / M_PI;
16     cout << "第三象限角abs3= " << abs3 << endl;
17     abs4 = atan2(-y, x) * 180 / M_PI;
18     cout << "第四象限角abs4= " << abs4 << endl;
19 
20     return 0;
21 }

输出结果：

第一象限角abs1= 0.572939
第二象限角abs2= 179.427
第三象限角abs3= -179.427
第四象限角abs4= -0.572939