 reserve L for AD_Lattice;
 reserve x,y,z for Element of L;

theorem Lem36c:
  x "/\" (y "/\" x) = y "/\" x
  proof
    for y, x be Element of L holds
      y "/\" (x "/\" y) = x "/\" y
    proof
      let y, x be Element of L;
      (x "/\" y) "\/" y = y by LemXX;
      hence thesis by DefA2;
    end;
    hence thesis;
  end;
