reserve L for Lattice;
reserve X,Y,Z,V for Element of L;
reserve L for D_Lattice;
reserve X,Y,Z for Element of L;
reserve L for 0_Lattice;
reserve X,Y,Z for Element of L;
reserve L for B_Lattice;
reserve X,Y,Z,V for Element of L;

theorem Th35:
  X "\/" (Y \ X) = X "\/" Y
proof
  X "\/" (Y \ X) = (X "\/" Y) "/\" (X "\/" X`) by LATTICES:11
    .= (X "\/" Y) "/\" Top L by LATTICES:21;
  hence thesis;
end;
