proposition: Lemma perp_mid_perp_bisect : forall A B C D, Midpoint C A B -> Perp C D A B -> Perp_bisect C D A B.
proof: Proof. intros. apply perp_bisect_equiv_def. unfold Perp_bisect_bis in *. exists C. split; auto. apply l8_14_2_1b_bis; Col. Qed.
imports: GeoCoq.Tarski_dev.Ch10_line_reflexivity_2