no goals
α : Type u_2
β : Type u_1
γ : Type ?u.73141
ι : Sort ?u.73144
ι' : Sort ?u.73147
f✝ : ι → α
s t : Set α
f : α → β
⊢ f '' s ∪ f '' sᶜ = range f
rw [← image_union, ← image_univ, ← union_compl_self]