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

Lemma lcos3_eq_trans : forall l1 a b c l2 d e f l3 g h i,
Eq_Lcos3 l1 a b c l2 d e f -> Eq_Lcos3 l2 d e f l3 g h i -> Eq_Lcos3 l1 a b c l3 g h i.