#include <bits/stdc++.h>
using namespace std;
const int N = 200005;
long long mod = 1000000009;
long long gcd(long long a, long long b) { return b == 0 ? a : gcd(b, a % b); }
long long lcm(long long a, long long b) { return a * (b / gcd(a, b)); }
bool is_vowel(char c) {
  if (c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u' || c == 'y')
    return 1;
  return 0;
}
double getDistance(double x1, double y1, double x2, double y2) {
  return sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
}
long long extended_euclidean(long long a, long long b, long long &x,
                             long long &y) {
  if (b == 0) {
    x = 1;
    y = 0;
    return a;
  }
  long long g = extended_euclidean(b, a % b, y, x);
  y -= (a / b) * x;
  return g;
}
long long power(long long base, long long p) {
  if (p == 1) return base;
  if (!p) return 1ll;
  long long ret = power(base, p / 2);
  ret *= ret;
  ret %= mod;
  if (p & 1) ret *= base;
  return ret % mod;
}
pair<int, int> vec(pair<int, int> a, pair<int, int> b) {
  pair<int, int> ret = pair<int, int>(a.first - b.first, a.second - b.second);
  return ret;
}
long long getArea(pair<int, int> a, pair<int, int> b, pair<int, int> c) {
  pair<int, int> x = vec(a, b);
  pair<int, int> y = vec(c, b);
  return abs(x.first * y.second - x.second * y.first);
}
int main() {
  double a, b, c, d, v, t, x[2], y[2];
  cin >> a >> b >> c >> d;
  cin >> v >> t;
  cin >> x[0] >> y[0] >> x[1] >> y[1];
  double low = 0.0, high = 10000000000;
  for (int i = (1); i <= (300); ++i) {
    double mid = (low + high) / 2.0;
    double X = a + min(mid, t) * x[0] + max(0.0, mid - t) * x[1];
    double Y = b + min(mid, t) * y[0] + max(0.0, mid - t) * y[1];
    double dist = getDistance(c, d, X, Y);
    if (v * mid - dist > 1e-9)
      high = mid;
    else
      low = mid;
  }
  printf("%.15f", low);
  return 0;
}
