| ⊦ a ∈ x ∪ y ∪ z ↔ a ∈ x ∪ z, a ∈ y |
⊦ a ∈ rmdup((x + y) + z) ↔ a ∈ rmdup(x + z), a ∈ y
Used simplifier rules: union: ⊦ x ∪ y = rmdup(x + y);%assoc: ⊦ (x ∪ y) ∪ z = x ∪ y ∪ z;%a: ⊦ (x + y) + z = x + y + z; from specification list% ⊦ rmdup(rmdup(x) + y) = rmdup(x + y); (s)