simp
α : Type u_1
G : group α
hmul_mem : ∀ (a b : α), a ∈ whole_group → b ∈ whole_group → a * b ∈ whole_group
hone_mem : has_one.one ∈ whole_group
a : α
a✝ : a ∈ whole_group
⊢ { isMember := fun x => True }.1 (group.inv a)
no goals