case a
α : Type u_1
inst✝ : DecidableEq α
𝒜 ℬ : Finset (Finset α)
s : Finset α
a : α
a✝ : Finset α
⊢ a✝ ∈ nonMemberSubfamily a (nonMemberSubfamily a 𝒜) ↔ a✝ ∈ nonMemberSubfamily a 𝒜
α : Type u_1
inst✝ : DecidableEq α
𝒜 ℬ : Finset (Finset α)
s : Finset α
a : α
⊢ nonMemberSubfamily a (nonMemberSubfamily a 𝒜) = nonMemberSubfamily a 𝒜
ext
no goals
case a
α : Type u_1
inst✝ : DecidableEq α
𝒜 ℬ : Finset (Finset α)
s : Finset α
a : α
a✝ : Finset α
⊢ a✝ ∈ nonMemberSubfamily a (nonMemberSubfamily a 𝒜) ↔ a✝ ∈ nonMemberSubfamily a 𝒜
simp