-- Mathlib/Combinatorics/SetFamily/AhlswedeZhang.lean
lemma card_truncatedSup_union_add_card_truncatedSup_infs (𝒜 ℬ : Finset (Finset α)) (s : Finset α) :
    #(truncatedSup (𝒜 ∪ ℬ) s) + #(truncatedSup (𝒜 ⊼ ℬ) s) =
      #(truncatedSup 𝒜 s) + #(truncatedSup ℬ s)

Proof state:
case pos
α : Type u_1
inst✝¹ : DecidableEq α
inst✝ : Fintype α
𝒜 ℬ : Finset (Finset α)
s : Finset α
h𝒜 : s ∈ lowerClosure ↑𝒜
hℬ : s ∈ lowerClosure ↑ℬ
⊢ #((𝒜 ∪ ℬ).truncatedSup s) + #((𝒜 ⊼ ℬ).truncatedSup s) = #(𝒜.truncatedSup s) + #(ℬ.truncatedSup s)

Tactic:
rw [truncatedSup_union h𝒜 hℬ, truncatedSup_infs h𝒜 hℬ]

Result:
case pos
α : Type u_1
inst✝¹ : DecidableEq α
inst✝ : Fintype α
𝒜 ℬ : Finset (Finset α)
s : Finset α
h𝒜 : s ∈ lowerClosure ↑𝒜
hℬ : s ∈ lowerClosure ↑ℬ
⊢ #(𝒜.truncatedSup s ⊔ ℬ.truncatedSup s) + #(𝒜.truncatedSup s ⊓ ℬ.truncatedSup s) =
    #(𝒜.truncatedSup s) + #(ℬ.truncatedSup s)

Proof state:
case pos
α : Type u_1
inst✝¹ : DecidableEq α
inst✝ : Fintype α
𝒜 ℬ : Finset (Finset α)
s : Finset α
h𝒜 : s ∉ lowerClosure ↑𝒜
hℬ : s ∈ lowerClosure ↑ℬ
⊢ #((𝒜 ∪ ℬ).truncatedSup s) + #((𝒜 ⊼ ℬ).truncatedSup s) = #(𝒜.truncatedSup s) + #(ℬ.truncatedSup s)

Tactic:
rw [truncatedSup_union_right h𝒜 hℬ, truncatedSup_of_not_mem h𝒜,
  truncatedSup_infs_of_not_mem fun h ↦ h𝒜 h.1, add_comm]

Result:
no goals

Proof state:
α : Type u_1
inst✝¹ : DecidableEq α
inst✝ : Fintype α
𝒜 ℬ : Finset (Finset α)
s : Finset α
⊢ #((𝒜 ∪ ℬ).truncatedSup s) + #((𝒜 ⊼ ℬ).truncatedSup s) = #(𝒜.truncatedSup s) + #(ℬ.truncatedSup s)

Tactic:
by_cases h𝒜 : s ∈ lowerClosure (𝒜 : Set <| Finset α) <;>
  by_cases hℬ : s ∈ lowerClosure (ℬ : Set <| Finset α)

Result:
case pos
α : Type u_1
inst✝¹ : DecidableEq α
inst✝ : Fintype α
𝒜 ℬ : Finset (Finset α)
s : Finset α
h𝒜 : s ∈ lowerClosure ↑𝒜
hℬ : s ∈ lowerClosure ↑ℬ
⊢ #((𝒜 ∪ ℬ).truncatedSup s) + #((𝒜 ⊼ ℬ).truncatedSup s) = #(𝒜.truncatedSup s) + #(ℬ.truncatedSup s)

case neg
α : Type u_1
inst✝¹ : DecidableEq α
inst✝ : Fintype α
𝒜 ℬ : Finset (Finset α)
s : Finset α
h𝒜 : s ∈ lowerClosure ↑𝒜
hℬ : s ∉ lowerClosure ↑ℬ
⊢ #((𝒜 ∪ ℬ).truncatedSup s) + #((𝒜 ⊼ ℬ).truncatedSup s) = #(𝒜.truncatedSup s) + #(ℬ.truncatedSup s)

case pos
α : Type u_1
inst✝¹ : DecidableEq α
inst✝ : Fintype α
𝒜 ℬ : Finset (Finset α)
s : Finset α
h𝒜 : s ∉ lowerClosure ↑𝒜
hℬ : s ∈ lowerClosure ↑ℬ
⊢ #((𝒜 ∪ ℬ).truncatedSup s) + #((𝒜 ⊼ ℬ).truncatedSup s) = #(𝒜.truncatedSup s) + #(ℬ.truncatedSup s)

case neg
α : Type u_1
inst✝¹ : DecidableEq α
inst✝ : Fintype α
𝒜 ℬ : Finset (Finset α)
s : Finset α
h𝒜 : s ∉ lowerClosure ↑𝒜
hℬ : s ∉ lowerClosure ↑ℬ
⊢ #((𝒜 ∪ ℬ).truncatedSup s) + #((𝒜 ⊼ ℬ).truncatedSup s) = #(𝒜.truncatedSup s) + #(ℬ.truncatedSup s)

Proof state:
case neg
α : Type u_1
inst✝¹ : DecidableEq α
inst✝ : Fintype α
𝒜 ℬ : Finset (Finset α)
s : Finset α
h𝒜 : s ∉ lowerClosure ↑𝒜
hℬ : s ∉ lowerClosure ↑ℬ
⊢ #((𝒜 ∪ ℬ).truncatedSup s) + #((𝒜 ⊼ ℬ).truncatedSup s) = #(𝒜.truncatedSup s) + #(ℬ.truncatedSup s)

Tactic:
rw [truncatedSup_of_not_mem h𝒜, truncatedSup_of_not_mem hℬ,
  truncatedSup_union_of_not_mem h𝒜 hℬ, truncatedSup_infs_of_not_mem fun h ↦ h𝒜 h.1]

Result:
no goals

Proof state:
case pos
α : Type u_1
inst✝¹ : DecidableEq α
inst✝ : Fintype α
𝒜 ℬ : Finset (Finset α)
s : Finset α
h𝒜 : s ∈ lowerClosure ↑𝒜
hℬ : s ∈ lowerClosure ↑ℬ
⊢ #(𝒜.truncatedSup s ⊔ ℬ.truncatedSup s) + #(𝒜.truncatedSup s ⊓ ℬ.truncatedSup s) =
    #(𝒜.truncatedSup s) + #(ℬ.truncatedSup s)

Tactic:
exact card_union_add_card_inter _ _

Result:
no goals

Proof state:
case neg
α : Type u_1
inst✝¹ : DecidableEq α
inst✝ : Fintype α
𝒜 ℬ : Finset (Finset α)
s : Finset α
h𝒜 : s ∈ lowerClosure ↑𝒜
hℬ : s ∉ lowerClosure ↑ℬ
⊢ #((𝒜 ∪ ℬ).truncatedSup s) + #((𝒜 ⊼ ℬ).truncatedSup s) = #(𝒜.truncatedSup s) + #(ℬ.truncatedSup s)

Tactic:
rw [truncatedSup_union_left h𝒜 hℬ, truncatedSup_of_not_mem hℬ,
  truncatedSup_infs_of_not_mem fun h ↦ hℬ h.2]

Result:
no goals