a ∈ rmdup(x), rmdup(x) = y + a ' + z ⊦ ¬ a ∈ y
a ∈ rmdup(x), rmdup(x) = y + a ' + z ⊦ ¬ a ∈ z
Used simplifier rules: rm-in-02: ⊦ a ∈ rmdup(x) ↔ a ∈ x;