(** The sum of two angles is equal to the sum of their two supplementary angles *)

(* Specifications: *)
Lemma bet2_suma__suma : forall A B C D E F G H I A' D', A' <> B -> D' <> E ->
Bet A B A' -> Bet D E D' -> SumA A B C D E F G H I -> SumA A' B C D' E F G H I.
Lemma suma_suppa2__suma : forall A B C D E F G H I A' B' C' D' E' F',
SuppA A B C A' B' C' -> SuppA D E F D' E' F' -> SumA A B C D E F G H I ->
SumA A' B' C' D' E' F' G H I.