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[数论] n+tan(n)无下界

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大一新生 Posted 2018-7-24 13:39 |Read mode
Last edited by 大一新生 2018-7-25 00:37遇到一个更难的问题,和这道题类似:
数列$\{x_n\}$满足$x_n=n+\tan n,n\in\mathbb N^{\ast}$,那么数列$\{x_n\}$是否有下界?

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hbghlyj Posted 2024-10-6 01:42
大一新生 发表于 2018-7-24 05:39
数列$\{x_n\}$满足$x_n=n+\tan n,n\in\mathbb N^{\ast}$,那么数列$\{x_n\}$是否有下界?
证明采用连分数逼近:Does the sequence n+tan(n),n∈N have a lower bound?

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hbghlyj Posted 2024-10-6 02:58
最后部分的证明很模糊
它说“So there are no reasons why the above conditions can make the required sequence limited.”但并没有真正证明满足条件的序列无限

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