
theorem Th3:
  for L being meet-absorbing join-absorbing join-associative
meet-commutative non empty LattStr, a, b being Element of L holds a [= a"\/"b
proof
  let L be meet-absorbing join-absorbing join-associative
meet-commutative
  non empty LattStr, a, b be Element of L;
  thus a"\/"( a"\/"b) = (a"\/"a)"\/"b by Def5
    .= a"\/"b;
end;
