2080.cpp

杭电 acm部分代码 有兴趣的可以下载 谢谢

#include <stdio.h>
#include <math.h>
int main()
{
	int n;
	scanf("%d",&n);
	double x1,y1;
	double x2,y2;
	double sum;
	double angle;
	while(n--)
	{
		scanf("%lf%lf%lf%lf",&x1,&y1,&x2,&y2);
        sum=x1*x2+y1*y2;
		angle=acos(double(sum/(sqrt(x1*x1+y1*y1)*sqrt(x2*x2+y2*y2))))/acos(-1*1.0)*180;
		printf("%.2lf\n",angle);		
	}
	return 0;
}