(3)dx.
解:(1)(x2+2x+3)dx
=x2dx+2xdx+3dx
=+x2+3x=.
(2)(sin x-cos x)dx
=sin xdx-cos xdx
=(-cos x)-sin x=2.
(3)dx=xdx+dx
=x2+ln x=×22-×12+ln 2-ln 1
=+ln 2.
3.求下列定积分:
(1) sin2dx;(2) (2-x2)·(3-x)dx.
解:(1)sin2=,
而′=-cos x,
∴sin2dx=dx
=
=-=.
(2)原式= (6-2x-3x2+x3)dx
=
=-
=-.