#include <bits/stdc++.h>
using namespace std;
const double eps = 1e-18;
double a, b, c, d, v, T, X1, Y1, X2, Y2;
double sol;
double dist(double a, double b, double c, double d) {
  return sqrt((c - a) * (c - a) + (d - b) * (d - b));
}
bool eq(double a, double b) { return fabs(a - b) < eps; }
bool check(double t) {
  double dd = t * v;
  double A, B;
  if (t < T) {
    A = a + t * X1;
    B = b + t * Y1;
  } else {
    A = a + T * X1 + (t - T) * X2;
    B = b + T * Y1 + (t - T) * Y2;
  }
  double D = dist(A, B, 1.0 * c, 1.0 * d);
  if (D < dd || eq(D, dd)) return 1;
  return 0;
}
int main() {
  cin.sync_with_stdio(false);
  cin >> a >> b >> c >> d;
  cin >> v >> T;
  cin >> X1 >> Y1;
  cin >> X2 >> Y2;
  double l = 0;
  double r = 1e18;
  for (int i = 1; i <= 10000; i++) {
    double mi = (l + r) / 2;
    if (check(mi)) {
      r = mi;
      sol = mi;
    } else
      l = mi;
  }
  cout << fixed << setprecision(18) << sol;
  return 0;
}
