proposition: Lemma g2_4 : forall A B C D, CongG A B C D -> CongG A B D C.
proof: Proof. intros A B C D HCong; apply g2_2; apply g2_3; apply g2_2; auto. Qed.
imports: GeoCoq.Axioms.tarski_axioms GeoCoq.Axioms.gupta_inspired_variant_axioms GeoCoq.Tarski_dev.Ch05_bet_le