proposition: Lemma not_par_not_col : forall A B C, A <> B -> A <> C -> ~Par A B A C -> ~Col A B C.
proof: Proof. intros. intro. apply H1. unfold Par. right. repeat split. assumption. assumption. apply col_trivial_1. Col. Qed.
imports: GeoCoq.Tarski_dev.Ch11_angles