theorem Th6:
  for L being join-absorbing join-commutative join-associative
meet-absorbing meet-commutative non empty LattStr, a, b, c being Element of L
  st a [= c & b [= c holds a "\/" b [= c
proof
  let L be join-absorbing join-commutative join-associative meet-absorbing
  meet-commutative non empty LattStr, a, b, c be Element of L;
  c"\/"c = c;
  hence thesis by Th4;
end;
