proposition: Lemma triangle_mid_par_flat : forall A B C P Q, B <> A -> Col A B C -> Midpoint P B C -> Midpoint Q A C -> Par A B Q P.
proof: Proof. intros. elim (midpoint_existence A B); intro R; intro. assert (HTMT := triangle_mid_par_flat_cong_aux A B C P Q R H H0 H1 H2 H3); spliter. assumption. Qed.
imports: GeoCoq.Tarski_dev.Annexes.quadrilaterals_inter_dec