reserve L for satisfying_DN_1 non empty ComplLLattStr;
reserve x, y, z for Element of L;

theorem Th36:
  for L being satisfying_DN_1 non empty ComplLLattStr, x, y, z
  being Element of L holds ((((x + y`) + z)` + y)` + (y` + y)`)` = y
proof
  let L be satisfying_DN_1 non empty ComplLLattStr;
  let x, y, z be Element of L;
  ((x + y`) + y)` = (y` + y)` by Th35;
  hence thesis by Th9;
end;
