#include<stdio.h>
#include<math.h>
double PI=3.141592653589793238462643383279502884197169399375105820974944592307816406286;
int main(){
int t,i;
scanf("%d",&t);
for(i=1;i<=t;i++){
double a1,a2,b1,b2,o1,o2,oa1,oa2,ob1,ob2,dot,oa,ob;
scanf("%lf%lf%lf%lf%lf%lf",&o1,&o2,&a1,&a2,&b1,&b2);
oa1=a1-o1;
oa2=a2-o2;
ob1=b1-o1;
ob2=b2-o2;
oa=pow(oa1*oa1+oa2*oa2,0.5);

dot=oa1*ob1+oa2*ob2;
ob=dot/(oa*oa);
printf("%0.6lf\n",(2*PI*oa*acos(ob))/(2*PI));


}






return 0;}