proposition: Lemma suppa__per : forall A B C, SuppA A B C A B C -> Per A B C.
proof: Proof. unfold SuppA. intros; spliter. ex_and H0 A'. apply l8_2, l11_18_2 with A'; trivial. apply conga_left_comm, H1. Qed.
imports: GeoCoq.Tarski_dev.Ch10_line_reflexivity_2