proposition: Lemma onc3__ncol : forall O P A B C, A <> B -> A <> C -> B <> C -> OnCircle A O P -> OnCircle B O P -> OnCircle C O P -> ~ Col A B C.
proof: Proof. intros. assert (Hcong := onc2__cong O P). apply (cong2__ncol O); Cong. Qed.
imports: GeoCoq.Tarski_dev.Ch12_parallel