#include <bits/stdc++.h>
using namespace std;
double a, b, c, d, vmax, t, w, x, y, z;
bool check(double mid) {
  double dist;
  if (mid <= t) {
    dist = 1.0 * (a + w * mid - c) * (a + w * mid - c) +
           1.0 * (b + x * mid - d) * (b + x * mid - d);
  } else {
    dist =
        1.0 * (a + w * t + y * (mid - t) - c) *
            (a + w * t + y * (mid - t) - c) +
        1.0 * (b + x * t + z * (mid - t) - d) * (b + x * t + z * (mid - t) - d);
  }
  return dist <= mid * mid * vmax * vmax;
}
int main() {
  scanf("%lf %lf %lf %lf", &a, &b, &c, &d);
  scanf("%lf %lf", &vmax, &t);
  scanf("%lf %lf %lf %lf", &w, &x, &y, &z);
  double lo = 0, hi = 1.0;
  while (!check(hi)) {
    lo = hi;
    hi *= 2;
  }
  while (abs(hi - lo) / max(1.0, lo) > 0.00000001) {
    double mid = (lo + hi) / 2;
    if (check(mid)) {
      hi = mid;
    } else {
      lo = mid;
    }
  }
  printf("%.10lf\n", lo);
  return 0;
}
