proposition: Lemma conga2_cop2__col_1 : forall A B C P P', ~ Col A B C -> CongA P B A P B C -> CongA P' B A P' B C -> Coplanar A B C P -> Coplanar A B C P' -> Col B P P'.
proof: Proof. intros A B C P P' HNCol HP HP' HCop HCop'. apply conga2_cop2__col with A C; trivial; [|apply coplanar_pseudo_trans with A B C; Cop..]. intro; apply HNCol; Col. Qed.
imports: GeoCoq.Tarski_dev.Ch10_line_reflexivity_2