x趋向0 lim(cot x- 1/x)=?
问题描述:
x趋向0 lim(cot x- 1/x)=?
答
x→0时cotx-1/x
=cosx/sinx-1/x
→(cosx-1)/x
=-2[sin(x/2)]/x
→-2(x/2)^2/x
=-x/2→0.