W

#include <iostream>
#include <iomanip>
#include <cmath>

using namespace std;

int main() {
    freopen("f.in", "r", stdin); freopen("f.out", "w", stdout);
    cin.tie(nullptr); cout.tie(nullptr);
    ios_base::sync_with_stdio(false);
    cout << setprecision(20);

    int x_1, y_1, x_2, y_2;
    int u, t;
    int v_x, v_y, w_x, w_y;
    cin >> x_1 >> y_1 >> x_2 >> y_2;
    cin >> u >> t;
    cin >> v_x >> v_y;
    cin >> w_x >> w_y;

    long long a, b, c, D;
    a = u * u - v_x * v_x - v_y * v_y;
    b = 2 * (v_x * (x_2 - x_1) + v_y * (y_2 - y_1));
    c = -((x_2 - x_1) * (x_2 - x_1) + (y_2 - y_1) * (y_2 - y_1));
    D = b * b - 4 * a * c;
    double t0 = (sqrt(D) - b) / (2 * a);
    if (t0 <= t) {
        cout << t0 << endl;
    } else {
        x_1 = x_1 + t * v_x - t * w_x;
        y_1 = y_1 + t * v_y - t * w_y;
        a = u * u - w_x * w_x - w_y * w_y;
        b = 2 * (w_x * (x_2 - x_1) + w_y * (y_2 - y_1));
        c = -((x_2 - x_1) * (x_2 - x_1) + (y_2 - y_1) * (y_2 - y_1));
        D = b * b - 4 * a * c;
        cout << (sqrt(D) - b) / (2 * a) << endl;
    }
}