#include <bits/stdc++.h>

using i64 = long long;

const double Pi = std::acos(-1.0);
constexpr double EPS = 1e-9;
double v, r, d;
double f(double x) {
    double s = std::sin(x);
    return 1 / v / (std::sqrt(s * s + 3) - s);
}
double simpson(double l, double r) {
    return (f(l) + 4 * f((l + r) / 2) + f(r)) * (r - l) / 6;
}
double integral(double l, double r, double eps, double st) {
    double mid = (l + r) / 2;
    double sl = simpson(l, mid);
    double sr = simpson(mid, r);
    if (std::abs(sl + sr - st) <= 15 * eps)
        return sl + sr + (sl + sr - st) / 15;
    return integral(l, mid, eps / 2, sl) + integral(mid, r, eps / 2, sr);
}
double integral(double l, double r) {
    return integral(l, r, EPS, simpson(l, r));
}
void solve() {
    std::cin >> v >> r >> d;
    r *= 2;
    
    auto check = [&](double t) {
        double x = d - v * t;
        assert(x - r >= r);
        double u = Pi - std::acos(r / (x - r));
        double ans = 0;
        double px = r - std::cos(u) * r;
        double py = std::sin(u) * r;
        double dis = std::sqrt((x - px) * (x - px) + py * py);
        ans += integral(0, u) * r;
        ans += dis * f(u);
        // std::cerr << t << " " << ans << " " << u << " " << integral(0, u) * r << " " << dis << " " << dis * f(u) << "\n";
        return ans <= t;
    };
    
    double ans = d / v;
    double lo = 0, hi = (d - 2 * r) / v - EPS;
    if (hi < lo) {
        std::cout << ans << "\n";
        return;
    }
    for (int _ = 0; _ < 100; _++) {
        double t = (lo + hi) / 2;
        if (check(t)) {
            hi = t;
        } else {
            lo = t;
        }
    }
    if (check(hi)) {
        ans = hi;
    }
    std::cout << ans << "\n";
}

int main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    
    std::cout << std::fixed << std::setprecision(10);
    
    int t;
    std::cin >> t;
    
    while (t--) {
        solve();
    }
    
    return 0;
}