#include <bits/stdc++.h>
using namespace std;
const double eps = 1e-8;
double dis(double x1, double y1, double x2, double y2) {
  return sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
}
double x_1, y_1, x2, y2, ex, ey;
double vx, vy, wx, wy;
double v, t;
int main() {
  scanf("%lf%lf%lf%lf", &x_1, &y_1, &x2, &y2);
  ex = x2 - x_1;
  ey = y2 - y_1;
  scanf("%lf%lf", &v, &t);
  scanf("%lf%lf%lf%lf", &vx, &vy, &wx, &wy);
  double l = 0, r = 1e20, mid;
  while (r - l > eps) {
    mid = (l + r) / 2.0;
    double nx = min(t, mid) * vx + max(mid - t, 0.0) * wx,
           ny = min(t, mid) * vy + max(mid - t, 0.0) * wy;
    if (dis(nx, ny, ex, ey) <= v * mid + eps)
      r = mid;
    else
      l = mid;
  }
  printf("%.7f\n", l);
  return 0;
}
