proposition: Lemma is_epi_pre_whisker_left_adjoint_counit_pointwise : ∏ x, isEpi (nat_trans_data_from_nat_trans εF x).
proof: Proof. intro x. assert (is0 : isEpi (nat_trans_data_from_nat_trans (Fη · εF) x)). { rewrite (maponpaths nat_trans_data_from_nat_trans triangle_eq_l). apply identity_isEpi. } apply (isEpi_precomp _ _ _ is0). Qed.
imports: UniMath.Foundations.All UniMath.MoreFoundations.All UniMath.CategoryTheory.Core.Categories UniMath.CategoryTheory.Core.Functors UniMath.CategoryTheory.Core.Isos UniMath.CategoryTheory.Core.NaturalTransformations UniMath.CategoryTheory.Epis UniMath.CategoryTheory.Epis UniMath.CategoryTheory.SplitMonicsAndEpis UniMath.CategoryTheory.Monics UniMath.CategoryTheory.FunctorCategory UniMath.CategoryTheory.whiskering