proposition: Lemma acute_distincts : forall A B C, Acute A B C -> A<>B /\ C<>B.
proof: Proof. intros A B C Hacute. destruct Hacute as [x [y [z [HPer Hlta]]]]. apply lta_distincts in Hlta. spliter. split; auto. Qed.
imports: GeoCoq.Tarski_dev.Ch10_line_reflexivity_2