proposition: Lemma acute_per__lta : forall A B C D E F, Acute A B C -> D <> E -> E <> F -> Per D E F -> LtA A B C D E F.
proof: Proof. intros A B C D E F Hacute HDE HEF HPer. intros. destruct Hacute as [G [H [I [HPer2 Hlta]]]]. assert(Hdiff := lta_distincts A B C G H I Hlta). spliter. apply (conga_preserves_lta A B C G H I); try (apply conga_refl); auto. apply l11_16; auto. Qed.
imports: GeoCoq.Tarski_dev.Ch10_line_reflexivity_2