reserve T for non empty RelStr,
  A,B for Subset of T,
  x,x2,y,z for Element of T;

theorem
  Fcl(A,2) = A^b^b
proof
  for B being Subset of T st B=(Fcl A).1 holds (Fcl A).(1+1)=B^b by Def2;
  then Fcl(A,2)=(Fcl(A,1))^b .=(A^b)^b by Th15;
  hence thesis;
end;
