#include <bits/stdc++.h>
using namespace std;
double dist(double a, double b, double c, double d) {
  return sqrt((a - c) * (a - c) + (b - d) * (b - d));
}
int main() {
  double x1, y1, x2, y2, vmax, t, vx, vy, wx, wy, xn, yn, ans = -1.0;
  cin >> x1 >> y1 >> x2 >> y2 >> vmax >> t >> vx >> vy >> wx >> wy;
  double beg = 0.0, end = t, mid;
  for (int i = 0; i < 100; i++) {
    mid = (beg + end) / 2;
    xn = x1 + mid * vx;
    yn = y1 + mid * vy;
    if (dist(xn, yn, x2, y2) / vmax <= mid)
      end = mid, ans = mid;
    else
      beg = mid;
  }
  if (ans != -1.0) {
    printf("%.7f", ans);
    return 0;
  }
  beg = t;
  end = 10e9;
  for (int i = 0; i < 1000; i++) {
    mid = (beg + end) / 2;
    xn = x1 + vx * t + (mid - t) * wx;
    yn = y1 + vy * t + (mid - t) * wy;
    if (dist(xn, yn, x2, y2) / vmax <= mid)
      end = mid, ans = mid;
    else
      beg = mid;
  }
  printf("%.7f", ans);
}
