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

Lemma lcos2_lg_not_null: forall lp l a b, Lcos2 lp l a b -> ~ Q_Cong_Null l /\ ~ Q_Cong_Null lp.