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

Lemma lcos3_lcos_2_1 : forall lp l a b c, Lcos3 lp l a b c <-> exists lab, Lcos2 lab l a b /\ Lcos lp lab c.