#include <bits/stdc++.h>
double M_PI = acos(-1);
struct point
{
    double x, y;
};
using namespace std;

int main()
{
    int N;
    cin >> N;

    vector<double> out;



    point mas[3];
    long double alpha, beta;
    for (int j = 0; j < N; j++)
    {
        for (int i = 0; i < 3; i++)
        {
            std::cin >> mas[i].x >> mas[i].y;
        }

        mas[1].x = mas[1].x - mas[0].x;
        mas[1].y = mas[1].y - mas[0].y;
        mas[2].x = mas[2].x - mas[0].x;
        mas[2].y = mas[2].y - mas[0].y;

        if (mas[1].y < 0) alpha = 2*M_PI + atan2l(mas[1].y, mas[1].x);
        else alpha = atan2l(mas[1].y, mas[1].x);

        if (mas[2].y < 0) beta = 2 * M_PI + atan2l(mas[2].y, mas[2].x);
        else beta = atan2l(mas[2].y, mas[2].x);

        //std::cout << '\n' << alpha << ' ' << beta << '\n';

        out.push_back(abs(alpha - beta));
    }

    cout << fixed;
    cout.precision(12);
    for (int i = 0; i < out.size(); i++)
    {
        cout << out[i] << '\n';
    }

    return 0;
}