#include <bits/stdc++.h>
using namespace std;
long double ax, bx, ay, by, vm, t, vx, vy, wx, wy;
long double sqr(long double a) { return a * a; }
long double dis(pair<long double, long double> a,
                pair<long double, long double> b) {
  return sqrt(sqr(a.first - b.first) + sqr(a.second - b.second));
}
bool check(long double rem) {
  long double new_x = ax + min(t, rem) * vx + max(rem - t, (long double)0) * wx;
  long double new_y = ay + min(t, rem) * vy + max(rem - t, (long double)0) * wy;
  return (dis({new_x, new_y}, {bx, by}) / rem <= vm);
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  cin >> ax >> ay >> bx >> by >> vm >> t >> vx >> vy >> wx >> wy;
  long double lo = 0, hi = 1e9, mid, ans;
  int iter = 500;
  while (iter--) {
    mid = (lo + hi) / 2;
    if (check(mid))
      hi = mid, ans = mid;
    else
      lo = mid;
  }
  cout << fixed << setprecision(6) << ans;
  return 0;
}
