设D:{9(O)srs2(O) c≤6≤B D f(rcos e, rsinOrdrde r=01( D B 2(6) do f(rose, rsin o) J1(O) 0() 0≤r≤((0 特别,对D 2a-r=(1(0) 0≤6<2丌 r=0(0) f(rcos 8, rsinOrdrdo D D q(6 do f(rcos e, sino)rdr Q团p  D o ( ) r =1  ( ) r =2  o ( )  r =1   ( )  r =2  ( ) ( ) 2 1 ( cos , sin ) d     f r  r  r r 设 , ( ) ( ) : 1 2             r   D 则 D f (r cos,rsin )r d r d  =   d 特别,对            0 2 0 ( ) : r D D f (r cos,rsin )r d r d  ( ) 0 ( cos , sin ) d   f r  r  r r  =   2 0 d r =( ) o D