reserve f, g, h for Function;
reserve x, y, z, u, X for set,
  A for non empty set,
  n for Element of NAT,
  f for Function of X, X;
reserve f for c=-monotone Function of bool X, bool X,
  S for Subset of X;

theorem Th8:
  S is_a_fixpoint_of f implies lfp(X,f) c= S & S c= gfp(X,f)
by Th6,Th7;
