proposition: Lemma tree_points_onc : forall O P, O <> P -> exists A B C, A <> B /\ A <> C /\ B <> C /\ OnCircle A O P /\ OnCircle B O P /\ OnCircle C O P.
proof: Proof. intros O P HOP. destruct (tree_points_onc_cop O P HOP) as [A [B [C]]]; spliter. exists A, B, C; repeat split; assumption. Qed.
imports: GeoCoq.Tarski_dev.Ch12_parallel