#include <bits/stdc++.h>
inline double pow(double a) { return a * a; }
int main() {
  double x1, y1, x2, y2, v, t, vx, vy, wx, wy;
  scanf("%lf %lf %lf %lf %lf %lf %lf %lf %lf %lf", &x1, &y1, &x2, &y2, &v, &t,
        &vx, &vy, &wx, &wy);
  double a = 0, b = 1e9;
  while (a + 1e-9 < b) {
    double m = (a + b) / 2;
    if (pow(x1 + m * vx - x2) + pow(y1 + m * vy - y2) < pow(v * m))
      b = m;
    else
      a = m;
  }
  if (a < t) {
    printf("%.9lf", a);
    return 0;
  }
  a = 0, b = 1e9;
  while (a + 1e-9 < b) {
    double m = (a + b) / 2;
    if (pow(x1 + t * vx + m * wx - x2) + pow(y1 + t * vy + m * wy - y2) <
        pow(v * (m + t)))
      b = m;
    else
      a = m;
  }
  printf("%.9lf", a + t);
  return 0;
}
