=-
=.
(2)因为cos=cos x+sin x,
所以dx=dx
=
=sin x-cos x
=-sin-
=-++=0.
(3)因为f(x)=|x+3|=
所以=
=+=5.
8.解:由题意可设切点A的坐标为(x0,x),
则切线方程为y=2x0x-x,可得切线与x轴的交点坐标为.画出草图,可得曲线y=x2,直线y=2x0x-x与x轴所围图形如图所示.
故S=S1+S2
=x2dx+[x2dx- (2x0x-x)dx]
=x3+x3-(x0x2-xx)
==,
解得x0=1,所以切点坐标为A(1,1),