#include <bits/stdc++.h>
using namespace std;
long long xs, ys;
long long xe, ye;
long long v, t;
long long vx, vy;
long long wx, wy;
int main() {
  cin >> xs >> ys;
  cin >> xe >> ye;
  cin >> v >> t;
  cin >> vx >> vy;
  cin >> wx >> wy;
  double l = 0.0;
  double r = 1e8;
  for (int i = 0; i < 100; ++i) {
    double mid = (l + r) / 2;
    double x = xs + min(mid, 1.0 * t) * vx + max(0.0, mid - t) * wx;
    double y = ys + min(mid, 1.0 * t) * vy + max(0.0, mid - t) * wy;
    x = abs(xe - x);
    y = abs(ye - y);
    if (x * x + y * y <= v * mid * v * mid) {
      r = mid;
    } else {
      l = mid;
    }
  }
  printf("%.9lf\n", l);
}
