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

theorem
  Finf(A,2) = A^f^f
proof
  Finf(A,2)=Finf(A,1+1) .=(Finf(A,1))^f by Def6
    .=A^f^f by Th33;
  hence thesis;
end;
