#include <bits/stdc++.h>
using namespace std;
double l, r;
int x, y, vx, vy, ux, uy, v, t, X, Y;
bool work(double time) {
  double ansx = x, ansy = y;
  if (time > t) {
    ansx -= vx * t + ux * (time - t);
    ansy -= vy * t + uy * (time - t);
  } else {
    ansx -= vx * time;
    ansy -= vy * time;
  }
  return ansx * ansx + ansy * ansy <= time * v * time * v;
}
int main() {
  scanf("%d%d%d%d", &X, &Y, &x, &y);
  x -= X;
  y -= Y;
  scanf("%d%d%d%d%d%d", &v, &t, &vx, &vy, &ux, &uy);
  l = 0;
  r = 200000000;
  while (r - l > 1e-6) {
    double mid = (l + r) / 2;
    if (work(mid))
      r = mid;
    else
      l = mid;
  }
  printf("%.14lf", l);
}
