F

#include <cmath>
#include <iostream>
using namespace std;

struct Point
{
    double x, y;
    Point(double x, double y)
    {
        this->x = x;
        this->y = y;
    }

    Point operator *(double k) const
    {
        return Point(x * k, y * k);
    }

    Point operator +(const Point& p) const
    {
        return Point(x + p.x, y + p.y);
    }
};

double getT(double x0, double y0, double a, double b, double x, double y, double v)
{
    double A = v * v - a * a - b * b;
    double B = -2 * (a * (x0 - x) + b * (y0 - y));
    double C = -(x0 - x) * (x0 - x) - (y0 - y) * (y0 - y);

    double D = B * B - 4 * A * C;

    double t = (-B + sqrt(D)) / (2 * A);
    return t;
}

double getT(Point a, Point da, Point c, double v)
{
    return getT(a.x, a.y, da.x, da.y, c.x, c.y, v);
}


double solve(Point a, Point b, Point da, Point db, Point c, double v)
{
    double t1 = getT(a, da, c, v);
    a = a + da * t1;
    b = b + db * t1;

    double t2 = getT(b, db, a, v);

    return t1 + t2;
}


int main(int argc, char* argv[])
{
    int x1, y1, dx1, dy1;
    int x2, y2, dx2, dy2;
    int x, y, v;

    scanf("%d%d%d%d", &x1, &y1, &dx1, &dy1);
    scanf("%d%d%d%d", &x2, &y2, &dx2, &dy2);
    scanf("%d%d%d", &x, &y, &v);

    Point a(x1, y1);
    Point da(dx1, dy1);

    Point b(x2, y2);
    Point db(dx2, dy2);

    Point c(x, y);

    double A = solve(a, b, da, db, c, v);
    double B = solve(b, a, db, da, c, v);

    double res = min(A, B);
    printf("%.11f\n", res);
}