#include <bits/stdc++.h>
using namespace std;
const double eps = 1e-9;
double X0, Y0, X1, Y1, vm, t, vx, vy, wx, wy, dx, dy;
int main() {
  scanf("%lf%lf%lf%lf", &X0, &Y0, &X1, &Y1);
  scanf("%lf%lf", &vm, &t);
  scanf("%lf%lf", &vx, &vy);
  scanf("%lf%lf", &wx, &wy);
  vx = -vx;
  vy = -vy;
  wx = -wx;
  wy = -wy;
  dx = X1 - X0;
  dy = Y1 - Y0;
  if (sqrt((dx + vx * t) * (dx + vx * t) + (dy + vy * t) * (dy + vy * t)) /
          vm <=
      t) {
    double low = 0, high = t, mid = (low + high) / 2;
    for (; high - low > eps; mid = (low + high) / 2)
      if (sqrt((dx + vx * mid) * (dx + vx * mid) +
               (dy + vy * mid) * (dy + vy * mid)) /
              vm <=
          mid)
        high = mid;
      else
        low = mid;
    printf("%.7lf\n", mid);
  } else {
    double low = t, high = 1e20, mid = (low + high) / 2;
    for (; high - low > eps; mid = (low + high) / 2) {
      if (sqrt((dx + vx * t + wx * (mid - t)) * (dx + vx * t + wx * (mid - t)) +
               (dy + vy * t + wy * (mid - t)) *
                   (dy + vy * t + wy * (mid - t))) /
              vm <=
          mid)
        high = mid;
      else
        low = mid;
    }
    printf("%.7lf\n", mid);
  }
  return 0;
}
