原题链接:http://acm.hdu.edu.cn/showproblem.php?pid=2080
#include <iostream>
#include "math.h"
using namespace std;
#define PI 3.14159265
double getTheta(double x, double y)
{
double th;
if(x==0)
th=90;
else if(y<0)
th=atan2(y, x)*180/PI+360;
else
th=atan2(y, x)*180/PI;
return th;
}
int main()
{
int t;
cin>>t;
double x1,y1,x2,y2;
while(t--)
{
cin>>x1>>y1>>x2>>y2;
double th1=getTheta(x1,y1);
double th2=getTheta(x2,y2);
//cout<<th1<<endl<<th2<<endl;
double th=th1-th2;
if(th<-180)
th=360+th;
else if(th<0)
th=-th;
else if(th<180)
th=th;
else
th=360-th;
printf("%.2f\n",th);
}
return 0;
}