#include <bits/stdc++.h>
using namespace std;
long double t(long double dx, long double dy, long double wx, long double wy,
              long double vMax) {
  long double a = vMax * vMax - wx * wx - wy * wy;
  long double bn = (dx * wx + dy * wy) / a;
  long double cn = (dx * dx + dy * dy) / a;
  return sqrt(bn * bn + cn) - bn;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  long double x1, y1, x2, y2;
  long double vMax, tWindChange;
  long double vx, vy;
  long double wx, wy;
  cin >> x1 >> y1 >> x2 >> y2 >> vMax >> tWindChange >> vx >> vy >> wx >> wy;
  long double t1 = t(x2 - x1, y2 - y1, vx, vy, vMax);
  if (t1 >= tWindChange) {
    t1 = t(x2 - x1 + tWindChange * (wx - vx), y2 - y1 + tWindChange * (wy - vy),
           wx, wy, vMax);
  }
  cout << fixed << setprecision(7) << t1;
}
