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. *)

Lemma out6_suma__suma : forall A B C D E F G H I A' C' D' F' G' I',
SumA A B C D E F G H I -> Out B A A' -> Out B C C' -> Out E D D' ->
Out E F F' -> Out H G G' -> Out H I I' -> SumA A' B C' D' E F' G' H I'.