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 ? )
A ? = A |^ 0 ,1 by Th79;
hence (A ? ) ^^ A = A ^^ (A ? ) by Th36; :: thesis: verum