| ∀ b, a. # s0 < 2 ∧ b ∈ s0 ∧ a ∈ s0 → a = b, #(s0 ++ a0) < 2, b ∈ s0 ++ a0, a ∈ s0 ++ a0 ⊦ a = b |
#(s0 ++ a0) < 2, ∀ b, a. # s0 < 2 ∧ b ∈ s0 ∧ a ∈ s0 → a = b, b = a0 ∨ b ∈ s0, a = a0 ∨ a ∈ s0 ⊦ a = b
Used simplifier rules: rax: ⊦ a ∈ s ++ b ↔ ¬ ¬(a = b ∨ a ∈ s);