proposition: Lemma per_suppa__per : forall A B C D E F, Per A B C -> SuppA A B C D E F -> Per D E F.
proof: Proof. unfold SuppA. intros; spliter. ex_and H1 A'. apply (l11_17 C B A'); [|apply conga_sym, H2]. apply conga_distinct in H2; spliter. apply per_col with A; Perp; Col. Qed.
imports: GeoCoq.Tarski_dev.Ch10_line_reflexivity_2