| ∀ y0, z0. rmdup(x0 + y0) \ z0 = rmdup((x0 \ z0) + (y0 \ z0)) ⊦ (a ∈ x0 ∨ a ∈ y ⊃ rmdup(x0 + y);a ' + rmdup(x0 + y)) \ z = rmdup((a ' + (x0 \ z)) + (y \ z)), a ∈ z |
a ∈ x0 ∨ a ∈ y, ∀ y0, z0. rmdup(x0 + y0) \ z0 = rmdup((x0 \ z0) + (y0 \ z0)) ⊦ rmdup(x0 + y) \ z = rmdup((a ' + (x0 \ z)) + (y \ z)), a ∈ z
¬(a ∈ x0 ∨ a ∈ y), ∀ y0, z0. rmdup(x0 + y0) \ z0 = rmdup((x0 \ z0) + (y0 \ z0)) ⊦ (a ' + rmdup(x0 + y)) \ z = rmdup((a ' + (x0 \ z)) + (y \ z)), a ∈ z