proposition: Lemma suma_assoc_2 : forall A B C D E F G H I K L M A' B' C' D' E' F', SAMS A B C D E F -> SAMS D E F G H I -> SumA A B C D E F A' B' C' -> SumA D E F G H I D' E' F' -> SumA A B C D' E' F' K L M -> SumA A' B' C' G H I K L M.
proof: Proof. intros A B C D E F G H I K L M A' B' C' D' E' F'. intros. apply suma_sym. apply (suma_assoc_1 G H I D E F A B C K L M D' E' F'); SumA. Qed.
imports: GeoCoq.Tarski_dev.Ch11_angles