#include<bits/stdc++.h>
using namespace std;
const double pi=acos(-1.0);
const double esp=1e-10;
struct point{//点/向量 
	double x,y;
	void in(){scanf("%lf %lf",&x,&y);}
	void out(){printf("%lf %lf\n",x,y);}
	point(double xx=0,double yy=0){x=xx,y=yy;}
};
double acs(double x){return acos(max(-1.0,min(1.0,x)));}
double f(double x){
	x=fabs(pi/2-x);
	return 1.0/(sqrt(4.0-sin(x)*sin(x))-cos(x));
} 
double simpson(double l,double r){
	double mid=(l+r)/2;
	return (f(l)+f(r)+4*f(mid))*(r-l)/6;
}
double s(double l,double r){
	double mid=(l+r)/2;
	double ansl=simpson(l,mid),ansr=simpson(mid,r);
	double ans=simpson(l,r);
	if(fabs(ans-ansl-ansr)<esp) return ansl+ansr;
	return s(l,mid)+s(mid,r);
}
double v,r,d;
bool check(double t)
{
	double x2=d-v*t;
	double ang=pi-acs(2.0*r/(x2-2*r));
	double t2=0,t3=0;
	t2+=2*r/v*s(0.0,ang);
	
	double a2=fabs(pi/2-ang);
	t3+=(x2-2*r)*cos(a2)/v/(sqrt(4.0-sin(a2)*sin(a2))-cos(a2));
	//printf("%lf %lf %lf ",t,t2,t3);
	return t2+t3<t;
}
void solve()
{
	scanf("%lf %lf %lf",&v,&r,&d);
	double L=0,R=(d-4*r)/v;
	while(R-L>esp)
	{
		//printf("%lf %lf\n",L,R);
		double mid=(L+R)/2;
		if(check(mid)) R=mid;
		else L=mid;
	}
	if(check(R)) printf("%.15lf\n",R);
	else printf("%.15lf\n",d/v);
	return;
}
int main()
{
	int t;scanf("%d",&t);
	while(t--) solve();
	return 0;
}