let x, E be set ; :: thesis: for A being Subset of st A ? = {x} holds
x = <%> E
let A be Subset of ; :: thesis: ( A ? = {x} implies x = <%> E )
A ? = A |^ 0 ,1 by Th79;
hence ( A ? = {x} implies x = <%> E ) by Th52; :: thesis: verum