#include <bits/stdc++.h>
using namespace std;
double x1, yy1, x2, y2, x3, y3, vx1, vx2, vy1, vy2, v, t, ans;
double dis(double xx, double yy) {
  return sqrt((xx - x2) * (xx - x2) + (yy - y2) * (yy - y2));
}
bool check1() {
  if (dis(vx1 * t + x1, vy1 * t + yy1) > v * t) return false;
  double l = 0, r = t, mid;
  while (r - l > 0.00000000001) {
    mid = (l + r) / 2;
    if (dis(vx1 * mid + x1, vy1 * mid + yy1) > v * mid)
      l = mid;
    else
      r = mid;
  }
  ans = mid;
  return true;
}
void check2() {
  double l = 0, r = INT_MAX, mid;
  while (r - l > 0.00000000001) {
    mid = (l + r) / 2;
    if (dis(vx2 * mid + x3, vy2 * mid + y3) > v * (mid + t))
      l = mid;
    else
      r = mid;
  }
  ans = mid + t;
}
int main() {
  scanf("%lf %lf %lf %lf", &x1, &yy1, &x2, &y2);
  scanf("%lf %lf", &v, &t);
  scanf("%lf %lf %lf %lf", &vx1, &vy1, &vx2, &vy2);
  x3 = x1 + vx1 * t;
  y3 = yy1 + vy1 * t;
  if (!check1()) check2();
  printf("%lf", ans);
  return 0;
}
