#include <bits/stdc++.h>
using namespace std;
int main(int argc, char const *argv[]) {
  long long x1, y1, x2, y2;
  scanf("%lld %lld %lld %lld", &x1, &y1, &x2, &y2);
  long long vm, t;
  scanf("%lld %lld", &vm, &t);
  long long vx, vy, wx, wy;
  scanf("%lld %lld %lld %lld", &vx, &vy, &wx, &wy);
  long long tx = x2 - vx * t - x1;
  long long ty = y2 - vy * t - y1;
  double l = 0, r = 1e8;
  int cnt = 0;
  long long det = tx * tx + ty * ty - vm * vm * t * t;
  if (det == 0) {
    printf("%lld\n", t);
  }
  if (det > 0) {
    x1 += vx * t;
    y1 += vy * t;
    vx = wx;
    vy = wy;
  }
  while (cnt < 64) {
    double m = (l + r) / 2;
    double px1 = vx * (det > 0 ? m - t : m) + x1;
    double py1 = vy * (det > 0 ? m - t : m) + y1;
    double px = x2 - px1;
    double py = y2 - py1;
    if (px * px + py * py > vm * vm * m * m) {
      l = m;
    } else {
      r = m;
    }
    cnt++;
  }
  printf("%.12f\n", l);
  return 0;
}
