#include <bits/stdc++.h>
double eps = 1e-12;
double dist(double ax, double ay, double bx, double by) {
  return sqrt((ax - bx) * (ax - bx) + (ay - by) * (ay - by));
}
int main() {
  int sx, sy, tx, ty;
  scanf("%d%d%d%d", &sx, &sy, &tx, &ty);
  int v, t;
  scanf("%d%d", &v, &t);
  int vx, vy, wx, wy;
  scanf("%d%d%d%d", &vx, &vy, &wx, &wy);
  double x = sx + t * vx, y = sy + t * vy;
  if (dist(x, y, (double)tx, (double)ty) / t < (double)v + eps) {
    double l = 0, r = t;
    for (int i = 1; i <= 100000; ++i) {
      double mid = (l + r) / 2.0;
      x = sx + mid * vx, y = sy + mid * vy;
      if (dist(x, y, (double)tx, (double)ty) / mid < (double)v + eps)
        r = mid;
      else
        l = mid;
    }
    printf("%.12f\n", l);
  } else {
    double l = t, r = 1e9;
    for (int i = 1; i <= 100000; ++i) {
      double mid = (l + r) / 2.0;
      x = sx + t * vx + (mid - t) * wx, y = sy + t * vy + (mid - t) * wy;
      if (dist(x, y, (double)tx, (double)ty) / mid < (double)v + eps)
        r = mid;
      else
        l = mid;
    }
    printf("%.12f\n", l);
  }
  return 0;
}
