#include <bits/stdc++.h>
using namespace std;
const int B = 8000000;
const long double PI = acos(-1);
int main(){
  cout << fixed << setprecision(20);
  auto calc = [&](long double x){
    return sqrt(1 + pow(sin(x), 2) / 3);
  };
  vector<long double> sum(B + 1);
  sum[0] = 0;
  for (int i = 0; i < B; i++){
    long double l = PI / B * i - PI;
    long double m = PI / B * (i + 0.5) - PI;
    long double r = PI / B * (i + 1) - PI;
    sum[i + 1] = sum[i] + (calc(l) + calc(m) * 4 + calc(r)) / 6 * (PI / B);
  }
  for (int i = 0; i <= B; i++){
    sum[i] /= sqrt(3);
    sum[i] += (cos(PI / B * i - PI) + 1) / 3;
  }
  int T;
  cin >> T;
  for (int i = 0; i < T; i++){
    long double v, r, d;
    cin >> v >> r >> d;
    long double T0 = r * 2 / v * sum[B];
    if (d < T0 * v){
      cout << d / v << endl;
    } else {
      int tv = B / 2, fv = B;
      while (fv - tv > 1){
        long double mid = (tv + fv) / 2;
        long double theta = PI / B * mid - PI;
        long double t = r * 2 / v * sum[mid];
        long double x = r * 2 + v * t + r * 2 * cos(theta);
        long double y = r * 2 * sin(theta);
        long double phi = atan2(-y, d - x);
        long double b = r * 4 * cos(theta) * (v * 2 * cos(phi) - v) + 8 * r * v * sin(theta) * sin(phi);
        if (b < 0){
          tv = mid;
        } else {
          fv = mid;
        }
      }
      long double theta = PI / B * tv - PI;
      long double t = r * 2 / v * sum[tv];
      long double x = r * 2 + v * t + r * 2 * cos(theta);
      long double y = r * 2 * sin(theta);
      long double ans = t + hypot(d - x, y) / (v * 2);
      cout << ans << endl;
    }
  }
}