theorem Th46:
  'not' Ex(Ex(a,A,G),B,G) '<' Ex(Ex('not' a,B,G),A,G)
proof
  'not' Ex(Ex(a,A,G),B,G) '<' Ex('not' All(a,B,G),A,G) by Th40;
  hence thesis by BVFUNC_2:18;
end;
