#include <bits/stdc++.h>
using namespace std;
int main() {
  long double x1, y1, x2, y2, v, t, vx, vy, wx, wy;
  cin >> x1 >> y1 >> x2 >> y2;
  cin >> v >> t >> vx >> vy >> wx >> wy;
  long double lb = 0, ub = 1e9;
  for (int i = 0; i < (int)(10000); i++) {
    long double mid = (lb + ub) / 2;
    complex<long double> vec =
        complex<long double>(x2, y2) - complex<long double>(x1, y1);
    vec -= complex<long double>(vx, vy) * min(t, mid);
    vec -= complex<long double>(wx, wy) * max(0.0L, mid - t);
    if (abs(vec) < v * mid)
      ub = mid;
    else
      lb = mid;
  }
  cout << setprecision(15) << fixed << lb << endl;
  return 0;
}
