Section Order.
Context `{T2D:Tarski_2D}.
Context `{TE:@Tarski_euclidean Tn TnEQD}.
(* sum_preserves leP : a <= x /\ b <= y => a + b <= x + y *)

Lemma square_pos : forall O E E' A A2,
O <> A -> Prod O E E' A A A2 -> Ps O E A2.