#include <bits/stdc++.h>
using namespace std;
double x2, y2, esp = 1e-7, v, t, vx, vy, wx, wy;
bool can(double m) {
  double t1 = min(t, m), t2 = max(0.0, m - t);
  double dx = x2 - vx * t1 - wx * t2;
  double dy = y2 - vy * t1 - wy * t2;
  return (v * m) * (v * m) >= dx * dx + dy * dy;
}
double binary(double l, double r) {
  if (r - l < esp) return l;
  double m = (l + r) / 2;
  if (can(m)) return binary(l, m);
  return binary(m, r);
}
int main() {
  double x1, y1;
  cin >> x1 >> y1 >> x2 >> y2;
  cin >> v >> t >> vx >> vy >> wx >> wy;
  x2 -= x1, y2 -= y1;
  printf("%.7f\n", binary(0, 1e18));
  return 0;
}
