一道高数求极限的题目lim(n→无穷大)n/(n^2+3)+n/(n^2+12)+...+n/(n^2+3n^2)=答案是√3·π/9,求详细步骤
问题描述：
一道高数求极限的题目
lim(n→无穷大)n/(n^2+3)+n/(n^2+12)+...+n/(n^2+3n^2)=
答案是√3·π/9,求详细步骤
答
用定积分来做
把分母上提出个n^2,所以
原极限=lim1/n* ∑1/[(1+3(k/n)^2]
=∫[1/(1+3x^2)]dx 积分区间o到1
=1/√3 arctan√3x| (o到1)
=1/√3（π/3-0)
=√3·π/9