1072 - Calm Down

#include<bits/stdc++.h>
using namespace std;
int main()
{
    int T,n,c=1;
    double R;
    scanf("%d",&T);
    while(T--)
    {
        scanf("%lf%d",&R,&n);
        printf("Case %d: %.10lf\n",c++,(R*sin(2*acos(0.0)/n))/(1+sin(2*acos(0.0)/n)));
 
    }
    return 0;
}