open Or in intro
| ⟨hs, inl ht⟩ => left; constructor; exact hs; exact ht
| ⟨hs, inr hu⟩ => right; constructor; exact hs; exact hu
case a.mp
α : Sort u_1
β : ?m.21867
γ : ?m.21870
s t u : Set α
x : α
⊢ x ∈ s.inter (t.union u) → x ∈ (s.inter t).union (s.inter u)
no goals