#include <bits/stdc++.h>
using namespace std;
int fx, fy, tx, ty;
double vmax;
double t;
double vx, vy, wx, wy;
double xx1, yy1, xx2, yy2;
double rr1, rr2;
double sqr(double k) { return k * k; }
double dis(double fx, double fy, double tx, double ty) {
  return sqrt(sqr(tx - fx) + sqr(ty - fy));
}
void bs1() {
  double l = 1e-11, r = t, mid, ans;
  ans = 0;
  while (r >= l + 1e-9) {
    mid = (l + r) / 2;
    xx1 = fx + vx * mid;
    yy1 = fy + vy * mid;
    rr1 = vmax * mid;
    if (dis(xx1, yy1, xx2, yy2) <= rr1) {
      ans = mid;
      r = mid;
    } else
      l = mid;
  }
  printf("%.17lf\n", ans);
}
void bs2() {
  double l = 1e-11, r = 1e11, mid, ans;
  ans = 0;
  while (r >= l + 1e-9) {
    mid = (l + r) / 2;
    xx2 = tx - wx * mid;
    yy2 = ty - wy * mid;
    rr2 = vmax * mid;
    if (dis(xx1, yy1, xx2, yy2) <= rr1 + rr2) {
      ans = mid;
      r = mid;
    } else
      l = mid;
  }
  printf("%.17lf\n", ans + t);
}
int main() {
  cin >> fx >> fy >> tx >> ty >> vmax >> t >> vx >> vy >> wx >> wy;
  xx1 = fx + vx * t;
  yy1 = fy + vy * t;
  rr1 = vmax * t;
  xx2 = tx;
  yy2 = ty;
  if (dis(xx1, yy1, xx2, yy2) <= rr1)
    bs1();
  else
    bs2();
  return 0;
}
