Section Suma_2.
Context `{TnEQD:Tarski_neutral_dimensionless_with_decidable_point_equality}.
(** ABC <= ABC + DEF. *)
(** DEF <= ABC + DEF. *)
(** LeA preserves SAMS. *)
(** SumA preserves LeA. *)
(** Unicity of the difference of angles. *)
(** Unicity of the difference on the left. *)
(** Associativity of the sum of angles. *)
(** If B <= B', E <= E' and B + E = B' + E', then B = B' and E = E' *)

Lemma sams_lea2_suma2__conga123 : forall A B C D E F G H I A' B' C' D' E' F',
LeA A B C A' B' C' -> LeA D E F D' E' F' -> SAMS A' B' C' D' E' F' ->
SumA A B C D E F G H I -> SumA A' B' C' D' E' F' G H I -> CongA A B C A' B' C'.