reserve n for Element of NAT,
  p,q,r,s for Element of HP-WFF;
reserve V for SetValuation;
reserve P for Permutation of V;

theorem Th34:
  Perm(P,p '&' q) = [:Perm(P,p),Perm(P,q):]
proof
  ex p9 being Permutation of SetVal(V,p), q9 being Permutation of SetVal(V,
  q) st p9 = (Perm P).p & q9 = (Perm P).q & (Perm P). (p '&' q) = [:p9,q9:] & (
  Perm P).(p => q) = p9 => q9 by Def5;
  hence thesis;
end;
