const In : set set prop term iIn = In infix iIn 2000 2000 term Subq = \x:set.\y:set.!z:set.z iIn x -> z iIn y const binintersect : set set set axiom binintersectE1: !x:set.!y:set.!z:set.z iIn binintersect x y -> z iIn x claim !x:set.!y:set.Subq (binintersect x y) x