proposition: Lemma lcos_lg_anga : forall l lp a, Lcos lp l a -> Lcos lp l a /\ Q_Cong l /\ Q_Cong lp /\ Q_CongA_Acute a.
proof: Proof. intros. split. auto. unfold Lcos in H. tauto. Qed.
imports: GeoCoq.Tarski_dev.Ch13_3_angles Morphisms