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

Lemma null_lcos : forall l a,Q_Cong l -> ~ Q_Cong_Null l -> Q_CongA_Null_Acute a -> Lcos l l a.