Proofgold Proof

pf
Let x0 of type ι be given. Assume H0: x0 ∈ real. Apply minus_SNo_minus_CSNo with x0, λ x1 x2 . x1 ∈ real leaving 2 subgoals. Apply real_SNo with x0. The subproof is completed by applying H0. Apply real_minus_SNo with x0. The subproof is completed by applying H0. ■