Section Cosinus2.
Context `{TnEQD:Tarski_neutral_dimensionless_with_decidable_point_equality}.
Global Instance lcos_morphism :
Proper (EqL ==> EqL ==> eq ==> iff) Lcos.
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Lemma lcos2_eq_lcos3_eq : forall la lb a b c d e, Q_CongA_Acute e -> Eq_Lcos2 la a b lb c d -> Eq_Lcos3 la a b e lb c d e.