proposition: Lemma isosceles_congaH : forall A B C, ~ColH A B C -> CongH A B A C -> CongaH A B C A C B.
proof: Proof. intros. apply (cong_5 A B C A C B). assumption. intro;apply H;Col. assumption. apply congH_sym;auto. apply ncolH_distincts in H;spliter;auto. apply conga_comm. intro;apply H;Col. Qed.
imports: Setoid Coq.Classes.Morphisms Coq.Classes.Morphisms_Prop GeoCoq.Axioms.gupta_inspired_variant_axioms GeoCoq.Meta_theory.Models.gupta_inspired_to_tarski GeoCoq.Tactics.Coinc.tactics_axioms GeoCoq.Tactics.Coinc.ColR GeoCoq.Meta_theory.Dimension_axioms.upper_dim_3 GeoCoq.Meta_theory.Parallel_postulates.parallel_postulates GeoCoq.Axioms.hilbert_axioms