
theorem Th13: :: 4.15
  for L being join-commutative join-associative Huntington non
  empty ComplLLattStr, a being Element of L holds a + Bot L = a
proof
  let L be join-commutative join-associative Huntington non empty
  ComplLLattStr, a be Element of L;
  a = (a` + a`)` + (a` + a)` by Def6
    .= a`` + (a` + a)` by Def7
    .= a + (a` + a)` by Th3;
  hence thesis by Th8;
end;
