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

Lemma lcos_eq_sym : forall la a lb b, Eq_Lcos la a lb b -> Eq_Lcos lb b la a.