#ifdef LOCAL
#define _GLIBCXX_DEBUG
#endif // LOCAL

#pragma GCC optimize("O3")
#include <bits/stdc++.h>
using namespace std;

using ll = long long;

using T = double;
const T pi = T(acosl(-1));

void solve_test (istream &cin, ostream &cout)
{
    int m, t;
    cin >> m >> t;

    T ans = 0;
    auto f = [&] (const int n)
    {
        if (n <= 2)
            return T(0);

        T len = T(t) / T(n) - T(m);
        if (len < 0)
            return T(0);

        return T(n) * len * len * 0.25 / T(tanl(pi / T(n)));
    };

    if (f(3) > T(0))
    {
        int left = 2, right = t;
        while (right - left > 1)
        {
            const int mid = (left + right) / 2;

            if (f(mid) >= f(mid + 1))
                right = mid;
            else
                left = mid;
        }

        for (int i = -3; i <= +3; i++)
        {
            ans = max(ans, f(left + i));
            ans = max(ans, f(right + i));
        }
    }

    cout << double(ans) << "\n";
}

void solve (istream &cin, ostream &cout)
{
    cout << fixed << setprecision(numeric_limits<double>::digits10);

    int t;
    cin >> t;

    for (int i = 0; i < t; i++)
        solve_test(cin, cout);
}

int main()
{
    #ifdef LOCAL
        ifstream in("input.txt");
        ofstream out("output.txt");
        solve(in, out);
    #else
        solve(cin, cout);
    #endif
}