#include <bits/stdc++.h>
using namespace std;
void main2(void) {}
void pre() {}
double x1, yyyasdfy12312, x2, y2, v, t, vx, vy, wx, wy;
double ki, ka, ans, mid;
double sqr(double x) { return x * x; }
bool cek(double a) {
  if (a <= t) {
    if (sqrt(sqr(fabs(x1 + a * vx - x2)) +
             sqr(fabs(yyyasdfy12312 + a * vy - y2))) <= v * a)
      return true;
    return false;
  } else {
    if (sqrt(sqr(fabs(x1 + t * vx + (a - t) * wx - x2)) +
             sqr(fabs(yyyasdfy12312 + t * vy + (a - t) * wy - y2))) <= v * a)
      return true;
    return false;
  }
}
int main() {
  scanf("%lf %lf %lf %lf", &x1, &yyyasdfy12312, &x2, &y2);
  scanf("%lf %lf", &v, &t);
  scanf("%lf %lf %lf %lf", &vx, &vy, &wx, &wy);
  ki = 0;
  ka = 2000000000;
  ans = 2000000000;
  for (int i = 0; i < 128; i++) {
    mid = (ki + ka) / 2;
    if (cek(mid)) {
      ans = min(ans, mid);
      ka = mid - 1e-7;
    } else {
      ki = mid + 1e-7;
    }
  }
  printf("%.10lf\n", ans);
}
