let E be set ; :: thesis: for A being Subset of (E ^omega) holds A ? = A |^ (0,1)
let A be Subset of (E ^omega); :: thesis: A ? = A |^ (0,1)
thus A ? = (A |^ 0) \/ (A |^ (0 + 1)) by Th75
.= A |^ (0,1) by Th28 ; :: thesis: verum