| # s0 + # s1 + 1 < #(s0 ∩ (s1 ++ a)), ∀ s0. ¬ # s0 + # s1 < #(s0 ∩ s1) ⊦ a ∈ s1 |
⊦ a ∈ s → s ∩ (s0 ++ a) = (s ∩ s0) ++ a
# s0 + # s1 + 1 < #(s0 ∩ (s1 ++ a)), ∀ s0. ¬ # s0 + # s1 < #(s0 ∩ s1) ⊦ a ∈ s1, a ∈ s0
# s0 + # s1 + 1 < #((s0 ∩ s1) ++ a), a ∈ s0, ∀ s0. ¬ # s0 + # s1 < #(s0 ∩ s1) ⊦ a ∈ s1
Used terms: a, s1, s0