#include <bits/stdc++.h>
using namespace std;

int const GOOD_ENOUGH=3000;

long double polygon_area(double p,int n){
  return (p*p/n)/(4*tanl(M_PI/n));
}

int main(){
  cerr.precision(40);
  cout.precision(40);

  int tn; cin>>tn; while (tn--){
    long long m,t; cin>>m>>t;

    pair<long double,int> best={0.L,0};
    for (int i=3; m*i<=t and i<=GOOD_ENOUGH; i++){
      best=max(best,{polygon_area(t-i*m,i),i});
    }
    cerr<<best.first<<" "<<best.second<<endl;
    cout<<best.first<<endl;
    assert(best.second<=2000);
  }
}