-- Mathlib/AlgebraicTopology/DoldKan/Compatibility.lean
theorem equivalenceCounitIso_eq (hη : τ₀ = τ₁ hF hG η) :
    (equivalence hF hG).counitIso = equivalenceCounitIso η

Proof state:
case w.app.h
A : Type u_1
A' : Type u_2
B : Type u_3
B' : Type u_4
inst✝³ : Category.{u_8, u_1} A
inst✝² : Category.{u_7, u_2} A'
inst✝¹ : Category.{u_6, u_3} B
inst✝ : Category.{u_5, u_4} B'
eA : A ≌ A'
eB : B ≌ B'
e' : A' ≌ B'
F : A ⥤ B'
hF : eA.functor ⋙ e'.functor ≅ F
G : B ⥤ A
hG : eB.functor ⋙ e'.inverse ≅ G ⋙ eA.functor
η : G ⋙ F ≅ eB.functor
hη : τ₀ = τ₁ hF hG η
Y : B
⊢ eB.inverse.map
        (F.map (eA.unitIso.hom.app (G.obj Y)) ≫
          F.map (eA.inverse.map (hG.inv.app Y)) ≫
            hF.inv.app (eA.inverse.obj (e'.inverse.obj (eB.functor.obj Y))) ≫
              e'.functor.map (eA.counitIso.hom.app (e'.inverse.obj (eB.functor.obj Y))) ≫
                e'.functor.map (hG.hom.app Y) ≫ hF.hom.app (G.obj Y) ≫ η.hom.app Y) ≫
      eB.unitIso.inv.app Y =
    eB.inverse.map (η.hom.app Y) ≫ eB.unitIso.inv.app Y

Tactic:
rw [hF.inv.naturality_assoc, hF.inv.naturality_assoc]

Result:
case w.app.h
A : Type u_1
A' : Type u_2
B : Type u_3
B' : Type u_4
inst✝³ : Category.{u_8, u_1} A
inst✝² : Category.{u_7, u_2} A'
inst✝¹ : Category.{u_6, u_3} B
inst✝ : Category.{u_5, u_4} B'
eA : A ≌ A'
eB : B ≌ B'
e' : A' ≌ B'
F : A ⥤ B'
hF : eA.functor ⋙ e'.functor ≅ F
G : B ⥤ A
hG : eB.functor ⋙ e'.inverse ≅ G ⋙ eA.functor
η : G ⋙ F ≅ eB.functor
hη : τ₀ = τ₁ hF hG η
Y : B
⊢ eB.inverse.map
        (hF.inv.app (G.obj Y) ≫
          (eA.functor ⋙ e'.functor).map (eA.unitIso.hom.app (G.obj Y)) ≫
            (eA.functor ⋙ e'.functor).map (eA.inverse.map (hG.inv.app Y)) ≫
              e'.functor.map (eA.counitIso.hom.app (e'.inverse.obj (eB.functor.obj Y))) ≫
                e'.functor.map (hG.hom.app Y) ≫ hF.hom.app (G.obj Y) ≫ η.hom.app Y) ≫
      eB.unitIso.inv.app Y =
    eB.inverse.map (η.hom.app Y) ≫ eB.unitIso.inv.app Y

Proof state:
case w.app.h
A : Type u_1
A' : Type u_2
B : Type u_3
B' : Type u_4
inst✝³ : Category.{u_8, u_1} A
inst✝² : Category.{u_7, u_2} A'
inst✝¹ : Category.{u_6, u_3} B
inst✝ : Category.{u_5, u_4} B'
eA : A ≌ A'
eB : B ≌ B'
e' : A' ≌ B'
F : A ⥤ B'
hF : eA.functor ⋙ e'.functor ≅ F
G : B ⥤ A
hG : eB.functor ⋙ e'.inverse ≅ G ⋙ eA.functor
η : G ⋙ F ≅ eB.functor
hη : τ₀ = τ₁ hF hG η
Y : B
⊢ eB.inverse.map
        (F.map
          (𝟙 (G.obj Y) ≫
            eA.unitIso.hom.app (G.obj Y) ≫
              eA.inverse.map (hG.inv.app Y) ≫ 𝟙 (eA.inverse.obj (e'.inverse.obj (eB.functor.obj Y))))) ≫
      (equivalence₂ eB hF).counitIso.hom.app Y =
    (equivalenceCounitIso η).hom.app Y

Tactic:
simp only [comp_id, id_comp, Functor.map_comp, equivalence₂CounitIso_eq,
  equivalence₂CounitIso_hom_app, assoc, equivalenceCounitIso_hom_app]

Result:
case w.app.h
A : Type u_1
A' : Type u_2
B : Type u_3
B' : Type u_4
inst✝³ : Category.{u_8, u_1} A
inst✝² : Category.{u_7, u_2} A'
inst✝¹ : Category.{u_6, u_3} B
inst✝ : Category.{u_5, u_4} B'
eA : A ≌ A'
eB : B ≌ B'
e' : A' ≌ B'
F : A ⥤ B'
hF : eA.functor ⋙ e'.functor ≅ F
G : B ⥤ A
hG : eB.functor ⋙ e'.inverse ≅ G ⋙ eA.functor
η : G ⋙ F ≅ eB.functor
hη : τ₀ = τ₁ hF hG η
Y : B
⊢ eB.inverse.map (F.map (eA.unitIso.hom.app (G.obj Y))) ≫
      eB.inverse.map (F.map (eA.inverse.map (hG.inv.app Y))) ≫
        eB.inverse.map (hF.inv.app (eA.inverse.obj (e'.inverse.obj (eB.functor.obj Y)))) ≫
          eB.inverse.map (e'.functor.map (eA.counitIso.hom.app (e'.inverse.obj (eB.functor.obj Y)))) ≫
            eB.inverse.map (e'.counitIso.hom.app (eB.functor.obj Y)) ≫ eB.unitIso.inv.app Y =
    eB.inverse.map (η.hom.app Y) ≫ eB.unitIso.inv.app Y

Proof state:
case w.app.h.e_a.e_a
A : Type u_1
A' : Type u_2
B : Type u_3
B' : Type u_4
inst✝³ : Category.{u_8, u_1} A
inst✝² : Category.{u_7, u_2} A'
inst✝¹ : Category.{u_6, u_3} B
inst✝ : Category.{u_5, u_4} B'
eA : A ≌ A'
eB : B ≌ B'
e' : A' ≌ B'
F : A ⥤ B'
hF : eA.functor ⋙ e'.functor ≅ F
G : B ⥤ A
hG : eB.functor ⋙ e'.inverse ≅ G ⋙ eA.functor
η : G ⋙ F ≅ eB.functor
hη : τ₀ = τ₁ hF hG η
Y : B
⊢ hF.inv.app (G.obj Y) ≫
      e'.functor.map
          (eA.functor.map (eA.unitIso.hom.app (G.obj Y)) ≫
            eA.counit.app (eA.functor.obj (G.obj Y)) ≫ 𝟙 (eA.functor.obj (G.obj Y))) ≫
        hF.hom.app (G.obj Y) ≫ η.hom.app Y =
    η.hom.app Y

Tactic:
rw [comp_id, eA.functor_unitIso_comp, e'.functor.map_id, id_comp, hF.inv_hom_id_app_assoc]

Result:
no goals

Proof state:
case w.app.h.e_a.e_a
A : Type u_1
A' : Type u_2
B : Type u_3
B' : Type u_4
inst✝³ : Category.{u_8, u_1} A
inst✝² : Category.{u_7, u_2} A'
inst✝¹ : Category.{u_6, u_3} B
inst✝ : Category.{u_5, u_4} B'
eA : A ≌ A'
eB : B ≌ B'
e' : A' ≌ B'
F : A ⥤ B'
hF : eA.functor ⋙ e'.functor ≅ F
G : B ⥤ A
hG : eB.functor ⋙ e'.inverse ≅ G ⋙ eA.functor
η : G ⋙ F ≅ eB.functor
hη : τ₀ = τ₁ hF hG η
Y : B
⊢ hF.inv.app (G.obj Y) ≫
      e'.functor.map
          (eA.functor.map (eA.unitIso.hom.app (G.obj Y)) ≫
            eA.counit.app (eA.functor.obj (G.obj Y)) ≫ 𝟙 ((G ⋙ eA.functor).obj Y)) ≫
        hF.hom.app (G.obj Y) ≫ η.hom.app Y =
    η.hom.app Y

Tactic:
dsimp

Result:
case w.app.h.e_a.e_a
A : Type u_1
A' : Type u_2
B : Type u_3
B' : Type u_4
inst✝³ : Category.{u_8, u_1} A
inst✝² : Category.{u_7, u_2} A'
inst✝¹ : Category.{u_6, u_3} B
inst✝ : Category.{u_5, u_4} B'
eA : A ≌ A'
eB : B ≌ B'
e' : A' ≌ B'
F : A ⥤ B'
hF : eA.functor ⋙ e'.functor ≅ F
G : B ⥤ A
hG : eB.functor ⋙ e'.inverse ≅ G ⋙ eA.functor
η : G ⋙ F ≅ eB.functor
hη : τ₀ = τ₁ hF hG η
Y : B
⊢ hF.inv.app (G.obj Y) ≫
      e'.functor.map
          (eA.functor.map (eA.unitIso.hom.app (G.obj Y)) ≫
            eA.counit.app (eA.functor.obj (G.obj Y)) ≫ 𝟙 (eA.functor.obj (G.obj Y))) ≫
        hF.hom.app (G.obj Y) ≫ η.hom.app Y =
    η.hom.app Y

Proof state:
case w.app.h
A : Type u_1
A' : Type u_2
B : Type u_3
B' : Type u_4
inst✝³ : Category.{u_8, u_1} A
inst✝² : Category.{u_7, u_2} A'
inst✝¹ : Category.{u_6, u_3} B
inst✝ : Category.{u_5, u_4} B'
eA : A ≌ A'
eB : B ≌ B'
e' : A' ≌ B'
F : A ⥤ B'
hF : eA.functor ⋙ e'.functor ≅ F
G : B ⥤ A
hG : eB.functor ⋙ e'.inverse ≅ G ⋙ eA.functor
η : G ⋙ F ≅ eB.functor
hη : τ₀ = τ₁ hF hG η
Y : B
⊢ eB.inverse.map (F.map (eA.unitIso.hom.app (G.obj Y))) ≫
      eB.inverse.map (F.map (eA.inverse.map (hG.inv.app Y))) ≫
        eB.inverse.map (hF.inv.app (eA.inverse.obj (e'.inverse.obj (eB.functor.obj Y)))) ≫
          eB.inverse.map (e'.functor.map (eA.counitIso.hom.app (e'.inverse.obj (eB.functor.obj Y)))) ≫
            eB.inverse.map (e'.counitIso.hom.app (eB.functor.obj Y)) ≫ eB.unitIso.inv.app Y =
    eB.inverse.map (η.hom.app Y) ≫ eB.unitIso.inv.app Y

Tactic:
simp only [← eB.inverse.map_comp_assoc, ← τ₀_hom_app, hη, τ₁_hom_app, equivalence₂_inverse,
  Functor.comp_obj]

Result:
case w.app.h
A : Type u_1
A' : Type u_2
B : Type u_3
B' : Type u_4
inst✝³ : Category.{u_8, u_1} A
inst✝² : Category.{u_7, u_2} A'
inst✝¹ : Category.{u_6, u_3} B
inst✝ : Category.{u_5, u_4} B'
eA : A ≌ A'
eB : B ≌ B'
e' : A' ≌ B'
F : A ⥤ B'
hF : eA.functor ⋙ e'.functor ≅ F
G : B ⥤ A
hG : eB.functor ⋙ e'.inverse ≅ G ⋙ eA.functor
η : G ⋙ F ≅ eB.functor
hη : τ₀ = τ₁ hF hG η
Y : B
⊢ eB.inverse.map
        (F.map (eA.unitIso.hom.app (G.obj Y)) ≫
          F.map (eA.inverse.map (hG.inv.app Y)) ≫
            hF.inv.app (eA.inverse.obj (e'.inverse.obj (eB.functor.obj Y))) ≫
              e'.functor.map (eA.counitIso.hom.app (e'.inverse.obj (eB.functor.obj Y))) ≫
                e'.functor.map (hG.hom.app Y) ≫ hF.hom.app (G.obj Y) ≫ η.hom.app Y) ≫
      eB.unitIso.inv.app Y =
    eB.inverse.map (η.hom.app Y) ≫ eB.unitIso.inv.app Y