Proofgold Proof

pf
Let x0 of type ι be given. Apply Empty_eq with setprod x0 0. Let x1 of type ι be given. Assume H0: x1 ∈ setprod x0 0. Apply EmptyE with ap x1 1. Apply ap1_Sigma with x0, λ x2 . 0, x1. The subproof is completed by applying H0. ■