#include <bits/stdc++.h>
using namespace std;
int INT_MAX_VAL = (int)0x3F3F3F3F;
int INT_MIN_VAL = (int)-0x3F3F3F3F;
long long LONG_MAX_VAL = (long long)0x3F3F3F3F3F3F3F3F;
long long LONG_MIN_VAL = (long long)-0x3F3F3F3F3F3F3F3F;
long long vx, vy, wx, wy;
long long R;
long double t;
bool solve(long double s, long double dx, long double dy) {
  if (s <= t) {
    dx -= vx * s;
    dy -= vy * s;
  } else {
    dx -= wx * (s - t) + vx * t;
    dy -= wy * (s - t) + vy * t;
  }
  return (dx * dx + dy * dy) <= (R * R * s * s);
}
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  long long x1, y1, x2, y2;
  cin >> x1 >> y1 >> x2 >> y2;
  cin >> R >> t;
  cin >> vx >> vy >> wx >> wy;
  long double l = 0;
  long double r = 1.0e9;
  while ((abs(r - l) / max(1.l, l)) > 1e-9) {
    double c = (l + r) / 2;
    if (solve(c, x2 - x1, y2 - y1)) {
      r = c;
    } else {
      l = c;
    }
  }
  cout << setprecision(15) << fixed << l << '\n';
  return 0;
}
