| # ax0 + 1 = # ay, unique_al(ay), b ∈ ay, unique_al(ax0), a ∈ ay, ∀ a0. a0 ∈ ax0 → a0 ∈ ay, ∀ ay0, b0. unique_al(ay0) ∧ # ax0 = # ay0 ∧ (∀ a. a ∈ ax0 → a ∈ ay0) ∧ b0 ∈ ay0 → b0 ∈ ax0 ⊦ b = a, b ∈ ax0, a ∈ ax0 |
⊦ a ∈ ax ↔ (∃ d, ay, az. ax = ay + (a × d)' + az)
# ax0 + 1 = # ay, unique_al(ay), b ∈ ay, unique_al(ax0), ∃ d, ay0, az. ay = ay0 + (a × d)' + az, ∀ a0. a0 ∈ ax0 → a0 ∈ ay, ∀ ay0, b0. unique_al(ay0) ∧ # ax0 = # ay0 ∧ (∀ a. a ∈ ax0 → a ∈ ay0) ∧ b0 ∈ ay0 → b0 ∈ ax0 ⊦ b = a, b ∈ ax0, a ∈ ax0
Used terms: ay, a