snakeerddd
幼苗
共回答了18个问题采纳率:88.9% 举报
lim(x趋向于0)(1/sinx)*((1/x)-(cosx/sinx))
=lim(x趋向于0)(sinx-xcosx)/ x sin^2x
=lim(x趋向于0)(sinx-xcosx)/ x ^3 ( x趋向于0时 sin^2x等价于x^2)
=lim(x趋向于0) [cosx-(cosx-xsinx)] / 3x^2 (洛必达)
=lim(x趋向于0) xsinx / 3x^2 ( x趋向于0时 xsinx等价于x^2)
=1/3
1年前
2