Proofgold Proof

pf
Let x0 of type ι be given. Let x1 of type ι → ο be given. Let x2 of type ι → ο be given. Assume H0: PNoEq_ x0 x1 x2. Let x3 of type ι be given. Assume H1: x3 ∈ x0. Apply iff_sym with x1 x3, x2 x3. Apply H0 with x3. The subproof is completed by applying H1. ■