Proofgold Proof

pf
Let x0 of type ι be given. Let x1 of type ι be given. Let x2 of type ι be given. Assume H0: ∀ x3 . x3 ∈ x0 ⟶ iff (x3 ∈ x1) (x3 ∈ x2). The subproof is completed by applying H0. ■