Definition sqrt3 := PythF 1 (PythF 1 1).

Lemma characterization_of_equality_F_bis : forall A B,
A = B <->
let (Ac, _) := coordinates_of_point_F A in
let (Ax, Ay) := Ac in
let (Bc, _) := coordinates_of_point_F B in
let (Bx, By) := Bc in
(Ax - Bx) * (Ax - Bx) + (Ay - By) * (Ay - By) =F= OF.