proposition: Lemma par_col4__par : forall A B C D E F G H, E <> F -> G <> H -> Par A B C D -> Col A B E -> Col A B F -> Col C D G -> Col C D H -> Par E F G H.
proof: Proof. intros A B C D E F G H. intros. apply (par_col2_par _ _ C D); auto. apply par_symmetry. apply (par_col2_par _ _ A B); auto. apply par_symmetry; auto. Qed.
imports: GeoCoq.Tarski_dev.Ch11_angles