Section Cosinus2.
Context `{TnEQD:Tarski_neutral_dimensionless_with_decidable_point_equality}.
Global Instance lcos_morphism :
Proper (EqL ==> EqL ==> eq ==> iff) Lcos.
(*----------------------------------------*)

Lemma lcos3_lg_anga : forall lp l a b c, Lcos3 lp l a b c -> Lcos3 lp l a b c /\ Q_Cong lp /\ Q_Cong l /\ Q_CongA_Acute a /\ Q_CongA_Acute b /\ Q_CongA_Acute c.