#include <bits/stdc++.h>
using namespace std;
int x, y, x2, y2, xx, yy;
double vm, t;
int main() {
  scanf("%d %d %d %d", &x, &y, &xx, &yy);
  xx -= x;
  yy -= y;
  scanf("%lf %lf", &vm, &t);
  scanf("%d %d", &x, &y);
  scanf("%d %d", &x2, &y2);
  double l = 0, r = 1E18;
  for (int i = (0); i <= (200); i++) {
    double m = (l + r) / 2;
    double px, py;
    if (m <= t) {
      px = xx - m * x;
      py = yy - m * y;
    } else {
      px = xx - t * x - (m - t) * x2;
      py = yy - t * y - (m - t) * y2;
    }
    if (px * px + py * py < m * m * vm * vm)
      r = m;
    else
      l = m;
  }
  printf("%.12lf\n", r);
  return 0;
}
