#include <bits/stdc++.h>
using namespace std;
double x1, yy1, x2, y2, v, t, vx, vy, wx, wy, l, r, mid, x, y, dis;
int main() {
  scanf("%lf%lf", &x1, &yy1);
  scanf("%lf%lf", &x2, &y2);
  scanf("%lf%lf", &v, &t);
  scanf("%lf%lf", &vx, &vy);
  scanf("%lf%lf", &wx, &wy);
  l = 0.0;
  r = 1e9;
  for (int i = 1; i <= 1000; ++i) {
    mid = (l + r) / 2;
    x = x2 - x1 - min(t, mid) * vx - max(0.0, mid - t) * wx;
    y = y2 - yy1 - min(t, mid) * vy - max(0.0, mid - t) * wy;
    dis = sqrt(x * x + y * y);
    if (v * mid > dis)
      r = mid;
    else
      l = mid;
  }
  printf("%.10lf\n", l);
  return 0;
}
