proposition: Lemma conga2_ghalfa__ghalfa : forall A B C A' B' C' D E F D' E' F', CongA A B C D E F -> CongA A' B' C' D' E' F' -> gHalfA A B C A' B' C' -> gHalfA D E F D' E' F'.
proof: Proof. intros A B C A' B' C' D E F D' E' F' HConga HConga1. rewrite 2 ghalfa_chara. intros [HAcute HSuma]. split. apply (acute_conga__acute A B C); assumption. apply (conga3_suma__suma A B C A B C A' B' C'); assumption. Qed.
imports: GeoCoq.Tarski_dev.Annexes.suma