我看了下书本，根本就看不懂。高数这门课，请教大家。

解:
(1).先求交点坐标,x=1与y=x-1的交点坐标为(1,0);y=2与y=x-1的交点坐标为(3,2);
即:D为: 1<x<3,x-1<y<2
∴(D)∫∫siny^2dxdy=(D)∫dx∫(2,x-1)siny^2dy
=(D)∫dx(ysiny^2-siny^2)|(2,x-1)
=(D)∫dx[2sin4-sin4-(x-1)xin(x-1)^2+sin(x-1)^2]
=(D)∫dxsin4-xsin(x-1)^2
=(D)∫(3,1) sin4-xsin(x-1)^2 dx
=xsin4|(3,1)-∫(3,1)xsin(x-1)^2dx
=3sin4-sin4-∫(3,1)x+1-1+sin(x-1)^2dx
=2sin4-∫(3,1)x-1+sin(x-1)^2dx-∫(3,1)dx
=2sin4-1/2∫(3,1)sin(x-1)^2d(x-1)^2-x|(3,1)
=2sin4-1/2cos(x-1)|(3,1)-(3-1)
=2sin4-2-1/2(cos2-cos0)
=2sin4-2-(cos2)/2+1/2
=2sin4-(cos2)/2-3/2
(2).
∵f(x)=sinx/x+C ∴f(x)ˊ=(sinx/x+C )ˊ=(xcosx-sinx)/x^2
∴∫xf(x)ˊdx=∫x*(xcosx-sinx)/x^2=∫cosx-sinx/xdx
=sinx-∫sinx/xdx
∫sinx/xdx= 多少再想一下