let E be set ; :: thesis: for A being Subset of holds A ^^ (A + ) = (A + ) ^^ A
let A be Subset of ; :: thesis: A ^^ (A + ) = (A + ) ^^ A
thus A ^^ (A + ) = A ^^ (A |^.. 1) by Th50
.= (A |^.. 1) ^^ A by Th23
.= (A + ) ^^ A by Th50 ; :: thesis: verum