Global Instance lcos_morphism :
 Proper (EqL ==> EqL ==> eq ==> iff) Lcos.

Lemma lcos2_eq_lcos3_eq : forall la lb a b c d e, Q_CongA_Acute e -> Eq_Lcos2 la a b lb c d -> Eq_Lcos3 la a b e lb c d e.