#include <bits/stdc++.h>
using namespace std;
int Vm;
int saodsasdasd, asdasdinaw, liahasdn, asldasndoasdhasd, t;
int vx, vy, wx, wy;
bool check(double T) {
  if (T - t <= 0.0000001) {
    if ((saodsasdasd - asdasdinaw + T * vx) *
                (saodsasdasd - asdasdinaw + T * vx) +
            (liahasdn - asldasndoasdhasd + T * vy) *
                (liahasdn - asldasndoasdhasd + T * vy) -
            (T * Vm) * (T * Vm) <=
        0.0000001)
      return true;
    else
      return false;
  } else {
    if ((saodsasdasd - asdasdinaw + t * (vx - wx) + T * wx) *
                (saodsasdasd - asdasdinaw + t * (vx - wx) + T * wx) +
            (liahasdn - asldasndoasdhasd + t * (vy - wy) + T * wy) *
                (liahasdn - asldasndoasdhasd + t * (vy - wy) + T * wy) -
            (T * Vm) * (T * Vm) <=
        0.0000001)
      return true;
    else
      return false;
  }
}
int main() {
  scanf("%d%d%d%d", &saodsasdasd, &liahasdn, &asdasdinaw, &asldasndoasdhasd);
  scanf("%d%d", &Vm, &t);
  scanf("%d%d", &vx, &vy);
  scanf("%d%d", &wx, &wy);
  double L = 0, R = 1000000000;
  double ans = 0;
  for (int i = 1; i <= 100; ++i) {
    double mid = (L + R) / 2;
    if (check(mid)) {
      ans = R = mid;
    } else
      L = mid;
  }
  printf("%.7f\n", ans);
  return 0;
}
