BBSecurity

#include <iostream>
#include <cmath>
#include <iomanip>
using namespace std;

int main()
{
    int n;
    cin>>n;
    int L,c,h;
    while(n--)
    {
        cin>>L>>c>>h;
        if(h==L)
        {
            cout<<c<<".00\n";
            continue;
        }
        double p=(double)(L-h);
        double q=(double)c*0.5,a,y,x;
        if(p==q)
        {
            cout<<"0.00\n";
            continue;
        }
        a=(double)((q+p)*(q-p))/(double)(2*p);
        y=q/a;
        x=2*a* asinh(y);
        if(x==(int)x)
            cout<<x<<".00\n";
        else
            cout<<fixed<<setprecision(2)<<x<<'\n';
    }
    return 0;
}