Section Sums.
Context `{TnEQD:Tarski_neutral_dimensionless_with_decidable_point_equality}.
(** Existence of the sum *)
(** Commutativity of the sum. *)
(** Unicity of the sum. *)

Lemma sums2__cong56 : forall A B C D E F E' F', SumS A B C D E F -> SumS A B C D E' F' ->
Cong E F E' F'.