let E be set ; :: thesis: for A being Subset of (E ^omega) holds (A +) ^^ (A ?) = A +
let A be Subset of (E ^omega); :: thesis: (A +) ^^ (A ?) = A +
thus (A +) ^^ (A ?) = (A |^.. 1) ^^ (A ?) by Th50
.= A |^.. 1 by Th41
.= A + by Th50 ; :: thesis: verum