⑩天掌 Teaching Plan on Advanced Mathematics o ∫R(x,y,2kd=』x,(x,yjrn R(x,y, z)dxdy=0. 于是』R(x,)d (RIx,y, 2(x, y)-Rx, v, ( x, y)ldxdy, OR dv=HR(x, y, z )dxdy tianjin polytechnic dmivendityTianjin Polytechnic University Teaching Plan on Advanced Mathematics ( , , ) [ , , ( , )] , 2 2   =  Dxy R x y z dxdy R x y z x y dxdy { [ , , ( , )] [ , , ( , )]} , =  2 − 1 Dxy R x y z x y R x y z x y dxdy   于是 R(x, y,z)dxdy ( , , ) 0. 3 =   R x y z dxdy( , , ) .     =    dv R x y z dxdy z R