#include <bits/stdc++.h>
using namespace std;
int main() {
  int T;
  scanf("%d", &T);
  while (T--) {
    double a, b, c;
    scanf("%lf%lf%lf", &a, &b, &c);
    printf("%.15lf\n", 1 / (1 / (a - b) + c * c * (a - b) / a / b));
  }
  return 0;
}
