(** If doubling two obtuse angles makes the same result, then these angles are congruent *)

Lemma suma2_obtuse2__conga : forall A B C D E F A' B' C',
Obtuse A B C -> SumA A B C A B C D E F ->
Obtuse A' B' C' -> SumA A' B' C' A' B' C' D E F ->
CongA A B C A' B' C'.