rw [← mem_coe, coe_mulStab hs, SetLike.mem_coe, mem_stabilizer_finset_iff_smul_finset_subset]
ι : Type u_1
α : Type u_2
inst✝¹ : Group α
inst✝ : DecidableEq α
s t : Finset α
a : α
hs : s.Nonempty
⊢ a ∈ s.mulStab ↔ a • s ⊆ s
no goals