Theorem: CategoryTheory.Monad.ForgetCreatesColimits.coconePoint_A
File: Mathlib/CategoryTheory/Monad/Limits.lean

Proof steps:
state_before: C : Type u₁
inst✝³ : Category.{v₁, u₁} C
T : Monad C
J : Type u
inst✝² : Category.{v, u} J
D : J ⥤ T.Algebra
c : Cocone (D ⋙ T.forget)
t : IsColimit c
inst✝¹ : PreservesColimit (D ⋙ T.forget) T.toFunctor
inst✝ : PreservesColimit ((D ⋙ T.forget) ⋙ T.toFunctor) T.toFunctor
⊢ T.η.app c.pt ≫ lambda c t = 𝟙 c.pt
state_after: C : Type u₁
inst✝³ : Category.{v₁, u₁} C
T : Monad C
J : Type u
inst✝² : Category.{v, u} J
D : J ⥤ T.Algebra
c : Cocone (D ⋙ T.forget)
t : IsColimit c
inst✝¹ : PreservesColimit (D ⋙ T.forget) T.toFunctor
inst✝ : PreservesColimit ((D ⋙ T.forget) ⋙ T.toFunctor) T.toFunctor
⊢ ∀ (j : J), c.ι.app j ≫ T.η.app c.pt ≫ lambda c t = c.ι.app j ≫ 𝟙 c.pt
tactic: apply t.hom_ext
state_before: C : Type u₁
inst✝³ : Category.{v₁, u₁} C
T : Monad C
J : Type u
inst✝² : Category.{v, u} J
D : J ⥤ T.Algebra
c : Cocone (D ⋙ T.forget)
t : IsColimit c
inst✝¹ : PreservesColimit (D ⋙ T.forget) T.toFunctor
inst✝ : PreservesColimit ((D ⋙ T.forget) ⋙ T.toFunctor) T.toFunctor
⊢ ∀ (j : J), c.ι.app j ≫ T.η.app c.pt ≫ lambda c t = c.ι.app j ≫ 𝟙 c.pt
state_after: C : Type u₁
inst✝³ : Category.{v₁, u₁} C
T : Monad C
J : Type u
inst✝² : Category.{v, u} J
D : J ⥤ T.Algebra
c : Cocone (D ⋙ T.forget)
t : IsColimit c
inst✝¹ : PreservesColimit (D ⋙ T.forget) T.toFunctor
inst✝ : PreservesColimit ((D ⋙ T.forget) ⋙ T.toFunctor) T.toFunctor
j : J
⊢ c.ι.app j ≫ T.η.app c.pt ≫ lambda c t = c.ι.app j ≫ 𝟙 c.pt
tactic: intro j
state_before: C : Type u₁
inst✝³ : Category.{v₁, u₁} C
T : Monad C
J : Type u
inst✝² : Category.{v, u} J
D : J ⥤ T.Algebra
c : Cocone (D ⋙ T.forget)
t : IsColimit c
inst✝¹ : PreservesColimit (D ⋙ T.forget) T.toFunctor
inst✝ : PreservesColimit ((D ⋙ T.forget) ⋙ T.toFunctor) T.toFunctor
j : J
⊢ c.ι.app j ≫ T.η.app c.pt ≫ lambda c t = c.ι.app j ≫ 𝟙 c.pt
state_after: C : Type u₁
inst✝³ : Category.{v₁, u₁} C
T : Monad C
J : Type u
inst✝² : Category.{v, u} J
D : J ⥤ T.Algebra
c : Cocone (D ⋙ T.forget)
t : IsColimit c
inst✝¹ : PreservesColimit (D ⋙ T.forget) T.toFunctor
inst✝ : PreservesColimit ((D ⋙ T.forget) ⋙ T.toFunctor) T.toFunctor
j : J
⊢ c.ι.app j = c.ι.app j ≫ 𝟙 c.pt
tactic: rw [show c.ι.app j ≫ T.η.app c.pt ≫ _ = T.η.app (D.obj j).A ≫ _ ≫ _ from
        T.η.naturality_assoc _ _,
      commuting, Algebra.unit_assoc (D.obj j)]
state_before: C : Type u₁
inst✝³ : Category.{v₁, u₁} C
T : Monad C
J : Type u
inst✝² : Category.{v, u} J
D : J ⥤ T.Algebra
c : Cocone (D ⋙ T.forget)
t : IsColimit c
inst✝¹ : PreservesColimit (D ⋙ T.forget) T.toFunctor
inst✝ : PreservesColimit ((D ⋙ T.forget) ⋙ T.toFunctor) T.toFunctor
j : J
⊢ c.ι.app j = c.ι.app j ≫ 𝟙 c.pt
state_after: no goals
tactic: simp
state_before: C : Type u₁
inst✝³ : Category.{v₁, u₁} C
T : Monad C
J : Type u
inst✝² : Category.{v, u} J
D : J ⥤ T.Algebra
c : Cocone (D ⋙ T.forget)
t : IsColimit c
inst✝¹ : PreservesColimit (D ⋙ T.forget) T.toFunctor
inst✝ : PreservesColimit ((D ⋙ T.forget) ⋙ T.toFunctor) T.toFunctor
⊢ T.μ.app c.pt ≫ lambda c t = T.map (lambda c t) ≫ lambda c t
state_after: C : Type u₁
inst✝³ : Category.{v₁, u₁} C
T : Monad C
J : Type u
inst✝² : Category.{v, u} J
D : J ⥤ T.Algebra
c : Cocone (D ⋙ T.forget)
t : IsColimit c
inst✝¹ : PreservesColimit (D ⋙ T.forget) T.toFunctor
inst✝ : PreservesColimit ((D ⋙ T.forget) ⋙ T.toFunctor) T.toFunctor
j : J
⊢ (T.mapCocone (T.mapCocone c)).ι.app j ≫ T.μ.app c.pt ≫ lambda c t =
    (T.mapCocone (T.mapCocone c)).ι.app j ≫ T.map (lambda c t) ≫ lambda c t
tactic: refine (isColimitOfPreserves _ (isColimitOfPreserves _ t)).hom_ext fun j => ?_
state_before: C : Type u₁
inst✝³ : Category.{v₁, u₁} C
T : Monad C
J : Type u
inst✝² : Category.{v, u} J
D : J ⥤ T.Algebra
c : Cocone (D ⋙ T.forget)
t : IsColimit c
inst✝¹ : PreservesColimit (D ⋙ T.forget) T.toFunctor
inst✝ : PreservesColimit ((D ⋙ T.forget) ⋙ T.toFunctor) T.toFunctor
j : J
⊢ (T.mapCocone (T.mapCocone c)).ι.app j ≫ T.μ.app c.pt ≫ lambda c t =
    (T.mapCocone (T.mapCocone c)).ι.app j ≫ T.map (lambda c t) ≫ lambda c t
state_after: C : Type u₁
inst✝³ : Category.{v₁, u₁} C
T : Monad C
J : Type u
inst✝² : Category.{v, u} J
D : J ⥤ T.Algebra
c : Cocone (D ⋙ T.forget)
t : IsColimit c
inst✝¹ : PreservesColimit (D ⋙ T.forget) T.toFunctor
inst✝ : PreservesColimit ((D ⋙ T.forget) ⋙ T.toFunctor) T.toFunctor
j : J
⊢ T.μ.app ((D ⋙ T.forget).obj j) ≫ (D.obj j).a ≫ c.ι.app j = T.map (D.obj j).a ≫ (D.obj j).a ≫ c.ι.app j
tactic: rw [Functor.mapCocone_ι_app, Functor.mapCocone_ι_app,
      show (T : C ⥤ C).map ((T : C ⥤ C).map _) ≫ _ ≫ _ = _ from T.μ.naturality_assoc _ _, ←
      Functor.map_comp_assoc, commuting, Functor.map_comp, Category.assoc, commuting]
state_before: C : Type u₁
inst✝³ : Category.{v₁, u₁} C
T : Monad C
J : Type u
inst✝² : Category.{v, u} J
D : J ⥤ T.Algebra
c : Cocone (D ⋙ T.forget)
t : IsColimit c
inst✝¹ : PreservesColimit (D ⋙ T.forget) T.toFunctor
inst✝ : PreservesColimit ((D ⋙ T.forget) ⋙ T.toFunctor) T.toFunctor
j : J
⊢ T.μ.app ((D ⋙ T.forget).obj j) ≫ (D.obj j).a ≫ c.ι.app j = T.map (D.obj j).a ≫ (D.obj j).a ≫ c.ι.app j
state_after: no goals
tactic: apply (D.obj j).assoc_assoc _