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: x2 ∈ setprod x0 x1. Apply proj1_Sigma with x0, λ x3 . x1, x2. The subproof is completed by applying H0. ■