#include <iomanip>
#include <cmath>
#include <iostream>
using namespace std;
int main()
{
    int n;
    float a, b, c, p, s;
    cout << fixed << setprecision(2);   //保留两位小数
    cin >> n;
    for(int i=0;i<n;i++)
    {
        cin >> a >> b >> c;
        if((a+b>c) && (a+c>b) && (b+c>a))
        {
            p = (a + b + c)/2;
            s = sqrt(p*(p-a)*(p-b)*(p-c));
            cout << s << endl;
        }
        else
            cout << "NaN" <<endl;
    }
    return 0;
}