51. 求极限 $\lim_{n\rightarrow\infty}\frac{1}{n}\sum_{i=1}^{n}\frac{i}{2^i}$.
Posted by haifeng on 2017-05-30 13:00:28 last update 2017-05-30 13:00:28 | Answers (1) | 收藏
求极限
\[
\lim_{n\rightarrow\infty}\frac{1}{n}(\frac{1}{2}+\frac{2}{2^2}+\frac{3}{2^3}+\cdots+\frac{n}{2^n})
\]