cos2X=1-2*(sinX)^2
lim(cos1/n)^n^2
=lim[(1-2sin^2(1/2n))^(-1/2sin^2(1/2n))]^[n^2*2sin^2(1/2n))]
=e^lim[n^2*2sin^2(1/2n))]
=e^(1/2)
lim (1+|x|)^1/x x->0
x>0且 x->0 lim (1+|x|)^1/x=e
x0 lim (1+|x|)^1/x=e^(-1)=1/e
故lim (1+|x|)^1/x x->0极限不存在