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 Th45:
  (X \ Y) \ Z = X \ (Y "\/" Z)
proof
  thus (X \ Y) \ Z = X "/\" (Y` "/\" Z`) by LATTICES:def 7
    .= X \ (Y "\/" Z) by LATTICES:24;
end;
