#include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  int x1, y1, x2, y2, v, t, vx, vy, wx, wy;
  cin >> x1 >> y1 >> x2 >> y2 >> v >> t >> vx >> vy >> wx >> wy;
  double lo = 0, hi = 2e8;
  for (int i = 1; i <= 1000; ++i) {
    double x, y, mid = (lo + hi) / 2;
    if (mid > t) {
      x = x1 + t * vx + (mid - t) * wx;
      y = y1 + t * vy + (mid - t) * wy;
    } else {
      x = x1 + mid * vx;
      y = y1 + mid * vy;
    }
    if (sqrt(pow(x2 - x, 2) + pow(y2 - y, 2)) <= mid * v)
      hi = mid;
    else
      lo = mid;
  }
  cout << setprecision(10) << lo << "\n";
  return 0;
}
