2在极坐标下有: ∫f(x,y)do=』(rcos,rsiO)rrd0 极坐标下的二重积分可用二次积分来计算 (1)若D:g1(0)≤r≤q2(O),a≤0≤B,则 (e) r=q1(6 02( D r=1(Q f f(rcos r sin O)rdrde=re derp(e)f(rcos e,rsin O)rdr2.在极坐标下有:  =  D D f (x, y)d f (r cos ,rsin )rdrd 极坐标下的二重积分可用二次积分来计算 (1)若D :1 ( )  r   2 ( ),     ,则 o x   ( ) r =  2  ( ) r = 1  x D o   ( ) r = 1  ( ) 2 r =   x o D  =               ( ) ( ) 2 1 f (r cos ,rsin )rdrd d f (r cos ,rsin )rdr D