no goals
α : Type u_2
β : Type u_1
γ : Type ?u.43908
ι : Sort ?u.43911
ι' : Sort ?u.43914
f✝ : α → β
s t : Set α
f : α → β
a b : α
⊢ f '' {a, b} = {f a, f b}
simp only [image_insert_eq, image_singleton]