case a
α : Type u_1
inst✝ : DecidableEq α
𝒜 ℬ : Finset (Finset α)
s : Finset α
a : α
a✝ : Finset α
⊢ a✝ ∈ memberSubfamily a (memberSubfamily a 𝒜) ↔ a✝ ∈ ∅
α : Type u_1
inst✝ : DecidableEq α
𝒜 ℬ : Finset (Finset α)
s : Finset α
a : α
⊢ memberSubfamily a (memberSubfamily 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✝ ∈ memberSubfamily a (memberSubfamily a 𝒜) ↔ a✝ ∈ ∅
simp