proposition: Lemma l11_43 : forall A B C, A <> B -> A <> C -> (Per B A C \/ Obtuse B A C) -> Acute A B C /\ Acute A C B.
proof: Proof. intros. split. apply l11_43_aux;auto. apply l11_43_aux;auto. induction H1. left;Perp. right;apply obtuse_sym;assumption. Qed.
imports: GeoCoq.Tarski_dev.Ch10_line_reflexivity_2