Section Suma_1.
Context `{TnEQD:Tarski_neutral_dimensionless_with_decidable_point_equality}.
(** Unicity of the sum. *)
(** Commutativity of the sum. *)
(** CongA preserves SumA. *)
(** Out preserves SumA. *)
(** ABC + 0 =  ABC (two lemmas) *)
(** 0 + DEF = DEF (two lemmas) *)

Lemma out213__suma : forall A B C D E F, D <> E -> E <> F -> Out B A C -> SumA A B C D E F D E F.