微积分问题1

1 secx = 1/cosx->；secx-1 =(1-cosx)/cosx x->0

2 1-cosx->；xx/2x-& gt；0

3 lim(secx-1)/(xx/2)= lim[(1-cosx)/cosx * 2/(xx)]

=lim[2(1-cosx)/xx]

=lim[2*(xx/2)/xx]

=1

所以secx-1相当于x ^ 2/2。