| ∀ a0. ¬ a0 ∈ s ∨ ¬ a0 ∈ s0 ++ a ⊦ a ∈ s, (¬ a0 ∈ s ∨ ¬ a0 ∈ s0) ∧ ¬ a ∈ s |
a0 ∈ s0, a0 ∈ s, a1 ∈ s0, a2 ∈ s, ∀ a1. ¬ a1 ∈ s ∨ ¬ a1 ∈ s0 ⊦ a ∈ s
Used simplifier rules: ⊦ ¬ a ∈ ∅; (s)% ⊦ s1 = s2 ↔ (∀ a. a ∈ s1 ↔ a ∈ s2); (s)%ne-01: ⊦ a ∈ s → s ≠ ∅; (forward) from specification set-basic% ⊦ a ∈ s ++ b ↔ a = b ∨ a ∈ s; (s)