#include <bits/stdc++.h>
using namespace std;
long double x, y, x2, y2, v, t, x3, y3, x4, y4;
bool check(long double a) {
  long double xx =
      min(a, (long double)t) * x3 + max((long double)0, a - t) * x4;
  long double yx =
      min(a, (long double)t) * y3 + max((long double)0, a - t) * y4;
  xx = abs(x2 - x - xx);
  yx = abs(y2 - y - yx);
  long double dis = sqrt(xx * xx + yx * yx);
  return dis <= a * v;
}
int main() {
  ios_base::sync_with_stdio(0);
  cin >> x >> y >> x2 >> y2 >> v >> t >> x3 >> y3 >> x4 >> y4;
  long double l = -1, r = 1e11;
  for (int i = 0; i < 500; i++) {
    long double mid = (l + r) / 2;
    if (check(mid))
      r = mid;
    else
      l = mid;
  }
  cout << fixed << setprecision(10) << r;
  return 0;
}
