#include <bits/stdc++.h>
using namespace std;
long double v, t, vx, vy, wx, wy, x1, x2, y11, y2;
bool f(long double tt) {
  long double x = x1, y = y11;
  if (tt > t) {
    x += t * vx + (tt - t) * wx;
    y += t * vy + (tt - t) * wy;
  } else {
    x += tt * vx;
    y += tt * vy;
  }
  long double dis = (x2 - x) * (x2 - x) + (y2 - y) * (y2 - y);
  dis = sqrt(dis);
  return dis < v * tt;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin >> x1 >> y11 >> x2 >> y2 >> v >> t >> vx >> vy >> wx >> wy;
  long double lo = 0, hi = 1e15, mid;
  for (int i = 0; i <= 300; i++) {
    mid = (lo + hi) / 2;
    if (f(mid))
      hi = mid;
    else
      lo = mid;
  }
  cout << fixed << setprecision(9) << lo;
  return 0;
}
