所以∫ 2 2 Zvx +y dude zr drdedz 2丌 de rdr zdz 0 0 =2兀 2-5)d 2 2丌 15 上一页下一页返回   = 1 1 0 2 2 0 r d r dr zdz    − = 1 0 2 2 ) 2 1 2 ( dr r  r . 15 2 =  =  zr drddz 2  +  z x y dxdydz 所以 2 2