const Subq : set set prop const setminus : set set set axiom setminus_Subq: !x:set.!y:set.Subq (setminus x y) x const In : set set prop term iIn = In infix iIn 2000 2000 const Power : set set axiom PowerI: !x:set.!y:set.Subq y x -> y iIn Power x claim !x:set.!y:set.setminus x y iIn Power x