高数夹逼定理证明

2025-04-14 05:01:18
推荐回答(3个)
回答1:

因为|xsinx/(x^2+1)|=|x||sinx|/(x^2+1),且-1<=|sinx|<=1
所以-|x|/(x^2+1)<=|xsinx/(x^2+1)|<=|x|/(x^2+1)
又因为-|xsinx/(x^2+1)|<=xsinx/(x^2+1)<=|xsinx/(x^2+1)|
所以-|x|/(x^2+1)<=xsinx/(x^2+1)<=|x|/(x^2+1)
因为lim(x->∞)±|x|/(x^2+1)=0
所以根据极限的夹逼性,lim(x->∞)xsinx/(x^2+1)=0

回答2:

0=lim-x/(x²+1)≤lim≤limx/(x²+1)=0

回答3:

-1