| ⊦ s ⊆ s0 ∧ s1 ⊆ s2 ∧ s3 ⊆ s4 → s ∪ s1 ∪ s3 ⊆ s0 ∪ s2 ∪ s4 |
∀ a. a ∈ s → a ∈ s0, ∀ a. a ∈ s1 → a ∈ s2, ∀ a. a ∈ s3 → a ∈ s4, a ∈ s ∨ a ∈ s1 ∨ a ∈ s3 ⊦ a ∈ s0, a ∈ s2, a ∈ s4
Used simplifier rules: unrax: ⊦ a ∈ s ∪ s0 ↔ ¬ ¬(a ∈ s ∨ a ∈ s0);%una: ⊦ (s ∪ s0) ∪ s1 = s ∪ s0 ∪ s1;%unc: ⊦ s ∪ s0 = s0 ∪ s;%Subset: ⊦ s1 ⊆ s2 ↔ (∀ a. a ∈ s1 → a ∈ s2); from specification set-basic