#include <bits/stdc++.h>
using namespace std;
const int INF = 1000001000;
const long long INFL = 2000000000000001000;
int solve();
int main() {
  srand(2317);
  cout.precision(10);
  cout.setf(ios::fixed);
  int tn = 1;
  for (int i = 0; i < tn; ++i) solve();
}
long double go(long double dx, long double dy, long double vx, long double vy,
               long double R) {
  long double D = hypotl(dx, dy);
  if (D == 0) return 0;
  long double rsinb = fabsl(vx * dy - vy * dx) / D;
  long double rcosb = sqrtl(max(0.L, R * R - rsinb * rsinb));
  long double v = rcosb + (vx * dx + vy * dy) / D;
  return D / v;
}
int solve() {
  long double x1, y1, x2, y2;
  cin >> x1 >> y1 >> x2 >> y2;
  long double vmax, t;
  cin >> vmax >> t;
  long double vx1, vy1;
  cin >> vx1 >> vy1;
  long double dx = x2 - x1;
  long double dy = y2 - y1;
  long double T = go(dx, dy, vx1, vy1, vmax);
  if (T <= t) {
    cout << T << '\n';
    return 0;
  }
  long double vx2, vy2;
  cin >> vx2 >> vy2;
  x2 -= (vx1 - vx2) * t;
  y2 -= (vy1 - vy2) * t;
  dx = x2 - x1;
  dy = y2 - y1;
  T = go(dx, dy, vx2, vy2, vmax);
  cout << T << '\n';
  return 0;
}
