#include <bits/stdc++.h>   using namespace std;   int main() {     double R, r, k;     int tt;     scanf( %d , &tt);     while (tt--) {       scanf( %lf%lf%lf , &R, &r, &k);       double a = (R + r) / (4 * R * r), b = k * (R - r) / (2 * R * r);       double t = (R - r) / (4 * R * r);       double s = t / (a * a + b * b - t * t);       printf( %.9lf n , s);     }     return 0;   }   