case cons a as h_ind =>
  dsimp [joinF.unitorLeftLax, joinF.unitorLeftOplax]
  rw [h_ind, Category.id_comp]
α : Type u
inst✝ : Category α
a : α
as : List α
h_ind : joinF.unitorLeftLax as ≫ joinF.unitorLeftOplax as = 𝟙 as
⊢ joinF.unitorLeftLax (a :: as) ≫ joinF.unitorLeftOplax (a :: as) = 𝟙 (a :: as)
no goals