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: nIn x2 x0. Assume H1: x2 ∈ setminus x0 x1. Apply H0. Apply setminusE1 with x0, x1, x2. The subproof is completed by applying H1. ■