水题堆2.U - 夹角有多大II

#include <stdio.h>
#include <math.h>

int main()
{
int t;
double x1,y1,x2,y2,a,b,c,pi=4*atan(1);
scanf("%d",&t);
while(t--){
scanf("%lf%lf%lf%lf",&x1,&y1,&x2,&y2);
a=y1/x1;
//else a=1;
b=y2/x2;
a=atan(a);
b=atan(b);

c=a>b?(a-b):(b-a);
c=c*180/pi;
// printf("%lf,\n",c);
if(y1*y2>0){
if(x1*x2<0)c=180-c;
}else
{
if(x1*x2<0){
c=180-c;
}
}
printf("%.2lf\n",c);
}
return 0;
}