| (s \ s0) ∩ s1 = ∅, a ∈ s2, a ∈ s1, ∀ a0. ¬ a0 ∈ s2 \ s ∨ ¬ a0 ∈ s1 ⊦ #((s2 \ s0) ∩ s1) = 0, # s2 = 0, # s1 = 0, s1 = ∅, s2 = ∅, a ∈ s0 |
⊦ s1 = s2 ↔ (∀ a. a ∈ s1 ↔ a ∈ s2)
a ∈ s1, a ∈ s2, ∀ a0. ¬ a0 ∈ s2 \ s ∨ ¬ a0 ∈ s1, ∀ a. a ∈ (s \ s0) ∩ s1 ↔ a ∈ ∅ ⊦ # s1 = 0, # s2 = 0, #((s2 \ s0) ∩ s1) = 0, s1 = ∅, s2 = ∅, a ∈ s0
Used terms: ∅, (s \ s0) ∩ s1