
theorem Th3: :: 4.10
  for L being join-commutative join-associative Huntington non
  empty ComplLLattStr, x being Element of L holds x`` = x
proof
  let L be join-commutative join-associative Huntington non empty
  ComplLLattStr, x be Element of L;
  set y = x`;
  (y`` + y`)` + (y`` + y)` = y` & (y + y``)` + (y + y`)` = x by Def6;
  hence thesis by Th2;
end;
