theorem Set.mem_image._simp_1
theorem Set.mem_image._simp_1: ∀ {α : Type u} {β : Type v} (f : α → β) (s : zpg9xh52.Set α) (y : β), Membership.mem (zpg9xh52.Set.image f s) y = ∃ x, Membership.mem s x ∧ f x = y
theorem Set.mem_image._simp_1
theorem Set.mem_image._simp_1: ∀ {α : Type u} {β : Type v} (f : α → β) (s : zpg9xh52.Set α) (y : β), Membership.mem (zpg9xh52.Set.image f s) y = ∃ x, Membership.mem s x ∧ f x = y