xcotx=x/tanx x→0则tanx的等价无穷小是x 所以极限=x/x=1,5,点击放大: ,2,lim(x->0)(xcotx)=lim(x->0)(xcosx/sinx) =lim(x->0)[(x/sinx)*cosx] =lim(x->0)(x/sinx)*lim(x->0)(cosx) =1*1 (应用重要极限lim(x->0)(sinx/x)=1) =1。,0,