#include <iostream>
# include <sstream>
# include <cmath>
# include <iomanip>
using namespace std;
double x,y,h;
bool check(double w){
    return h/sqrt(x*x-w*w)+h/sqrt(y*y-w*w)-1>=0; //单调递减函数
}
int main() {
    int t;
    cin>>t;
    for(int i=0;i<t;i++){
        cin>>x>>y>>h;
        double l=0;
        double r=x<y?x:y;
        while(r-1>1e-12){
            double mid = (l+r)/2;
            if(check(mid))r=mid; //如果在x轴上方则向右查找
            else{
                l = mid;
            }
        }
        cout<<fixed<<setprecision(6)<<i<<": "<<r;
    }
}

std::pair<int, int> getElem(int a,list *l1)
{

    list *b=l1;
    int count=0;
    for(;b->next!=NULL;b=b->next){
        if(a==b->a){
            return std::pair<int, int>(a,count); //返回元素和下标
        }
        count++;
    }
    if(b->a==a){
        return std::pair<int, int>(a,count); //未找到返回-1
    }
    return std::pair<int, int>(a,-1);
    
}