(2)若D:0≤r≤p(0),c≤≤B,则 qp(6) ∫ f(rcos 6, rsin O)rdrd8 D re depot)f(rcos 8 singra (3)此时D:0≤r≤q(0,0≤0≤2m,且 Oy(0) ∫ f(rcos(, rsin 6) )rare D fo defo f(rcos e, sino)rdr K心(2)若D : 0  r  ( ),     ,则 x o D   r = ( )    =           ( ) 0 ( cos , sin ) ( cos , sin ) d f r r rdr f r r rdrd D D o x r = ( ) (3)此时D : 0  r  ( ),0    2 ,且    =          2 0 ( ) 0 ( cos , sin ) ( cos , sin ) d f r r rdr f r r rdrd D