intro
| inl ⟨hs,ht⟩ => constructor; left; exact hs; left; exact ht
| inr hu => constructor; right; exact hu; right; exact hu
case a.mp
α : Sort u_1
β : ?m.21318
γ : ?m.21321
s t u : Set α
x : α
⊢ x ∈ (s.inter t).union u → x ∈ (s.union u).inter (t.union u)
no goals