lim(x->0)(1-cosx+sinx)/x
=lim(x->0)(1-cosx)/x+lim(x->0)(sinx)/x
=lim(x->0)(x方/2)/x+lim(x->0)(x)/x
=0+1
=1
所以
x->0时 1-cosx+sinx~xlim[ (1-cosx)/x + sinx/x ]
可以分别将1-cosx和sinx用等价无穷小替换吗1-cosx~x方/2
sinx~x