如图所示
x->0+
分子
√cosx
=√ [ 1- (1/2)x^2 +o(x^2) ]
=1 - (1/4)x^2 +o(x^2)
1-√cosx =(1/4)x^2 +o(x^2)
分母
cos√x
= 1- (1/2)(√x)^2 + o(x)
= 1- (1/2)x + o(x)
1-cos√x =(1/2)x + o(x)
x(1-cos√x) =(1/2)x^2 + o(x^2)
lim(x->0+) (1-√cosx)/[x(1-cos√x) ]
=lim(x->0+) (1/4)x^2 /[(1/2)x^2 ]
=1/2
如图
这是参考过程