theorem Th40:
  H is conjunctive implies H = (the_left_argument_of H) '&'
  the_right_argument_of H
proof
  assume
A1: H is conjunctive;
  then ex F1 st H = (the_left_argument_of H) '&' F1 by Def31;
  hence thesis by A1,Def32;
end;
