#include <bits/stdc++.h>
using namespace std;
int main() {
  cin.tie(0);
  ios_base::sync_with_stdio(0);
  double start_x, start_y, end_x, end_y;
  cin >> start_x >> start_y >> end_x >> end_y;
  double speed, t;
  cin >> speed >> t;
  double v_x, v_y, w_x, w_y;
  cin >> v_x >> v_y >> w_x >> w_y;
  double low = 0;
  double high = 1e9;
  while (high - low >= 1.0 / 1e8) {
    double T = (low + high) / 2;
    double d_x = v_x * min(T, t) + w_x * max(0.0, T - t);
    double d_y = v_y * min(T, t) + w_y * max(0.0, T - t);
    double total_x = (start_x + d_x - end_x);
    double total_y = (start_y + d_y - end_y);
    if (T * speed >= sqrt(total_x * total_x + total_y * total_y)) {
      high = T;
    } else {
      low = T;
    }
  }
  std::cout << std::setprecision(15) << (low + high) / 2 << std::endl;
}
