#include<iostream>
#include<stdio.h>
#include<algorithm>
#include<string.h>
#include<math.h>
#include<queue>
#include<stack>
#define ll long long
#define pi acos(-1)
using namespace std;
struct node
{
double x,y,v,r;
}p,Q,h,D;
double mid,l,r,alp,thelen;
double l1,l2,l3,a1;
double dis(node a,node b)
{
return sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));
}
bool CorssTheCircle(node a,node b)
{
double d1=fabs(a.x*b.y-b.x*a.y)/dis(a,b),d2,d3,d4;
if (a1<1e-10 || d1-Q.r>-1e-10) return true;
return false;
}
double judge(double t)
{
double a=p.v*t+alp,t1;
h.x=p.r*cos(a);
h.y=p.r*sin(a);
l1=(Q.x*Q.x)+(Q.y*Q.y);
l2=(h.x*h.x)+(h.y*h.y);
l3=(Q.x-h.x)*(Q.x-h.x)+(Q.y-h.y)*(Q.y-h.y);
a1=acos((l1+l2-l3)/(2*sqrt(l1)*sqrt(l2)))-acos(Q.r/sqrt(l1))-acos(Q.r/sqrt(l2));
if (CorssTheCircle(Q,h)) t1=dis(h,Q);
else t1=sqrt(l1-Q.r*Q.r)+sqrt(l2-Q.r*Q.r)+thelen*a1/(2*pi);
t1/=Q.v;
if (t1<t) return false;
return true;
}
int main()
{
while (~scanf("%lf%lf%lf",&p.x,&p.y,&p.v))
{
scanf("%lf%lf%lf%lf",&Q.x,&Q.y,&Q.v,&Q.r);
thelen=2*pi*Q.r;
p.r=sqrt(p.x*p.x+p.y*p.y);
D.x=D.y=0;
alp=acos(p.x/p.r);
if (p.y<0) alp=-alp;
p.v/=p.r;
l=0; r=1e+10;
while (r-l>1e-12)
{
mid=(l+r)*0.5;
if (judge(mid)) l=mid;
else r=mid;
}
printf("%.9lf\n",l);
}
return 0;
}