Configurations in the Euclidean plane associated to a system of equations

Francesco Colangelo

In the Euclidean plane ${\mathbf{E}}^2$, fix four pairwise distinct points \begin{equation*} \label{eqA} \begin{array}{ccc} A=(a_1,a_2),\ B=(b_1,b_2),\ C=(c_1,c_2),\ D=(d_1,d_2), \end{…