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  • RE: 哈基 项目推荐

  • RE: 哈基 项目推荐

    VPS重装脚本

  • RE: Why the harmonic series diverges

    $$\sum_{n=1}^{\infty}\frac{1}{n^2}=\frac{\pi^2}{6}$$

  • RE: Why the harmonic series diverges

    $$\sum_{n=1}^{\infty}\frac{1}{n^2}=\frac{\pi^2}{6}$$

  • RE: Why the harmonic series diverges

    Inline double escaped: \(x^2+1\)

    Block dollars:

    $$
    \sum_{n=1}^{\infty}\frac{1}{n^2}=\frac{\pi^2}{6}
    $$

  • Why the harmonic series diverges

    One of the first beautiful surprises in analysis is that the harmonic series diverges, even though its terms go to zero.

    The series is

    $$
    1 + \frac{1}{2} + \frac{1}{3} + \frac{1}{4} + \frac{1}{5} + \cdots
    $$

    At first it feels like it should converge, because the terms (1/n) become smaller and smaller. But the condition (a_n \to 0) is necessary for convergence, not sufficient.

    The classic grouping argument is very neat:

    $$
    1 + \frac{1}{2}

    • \left(\frac{1}{3} + \frac{1}{4}\right)
    • \left(\frac{1}{5} + \cdots + \frac{1}{8}\right)
    • \left(\frac{1}{9} + \cdots + \frac{1}{16}\right)
    • \cdots
      $$

    Now look at each group.

    For the group

    $$
    \frac{1}{3} + \frac{1}{4},
    $$

    both terms are at least (1/4), so

    $$
    \frac{1}{3} + \frac{1}{4} \geq \frac{1}{4} + \frac{1}{4} = \frac{1}{2}.
    $$

    For the next group,

    $$
    \frac{1}{5} + \frac{1}{6} + \frac{1}{7} + \frac{1}{8},
    $$

    all four terms are at least (1/8), so

    $$
    \frac{1}{5} + \frac{1}{6} + \frac{1}{7} + \frac{1}{8}
    \geq 4 \cdot \frac{1}{8}
    = \frac{1}{2}.
    $$

    In general, the group

    $$
    \frac{1}{2^k+1} + \frac{1}{2^k+2} + \cdots + \frac{1}{2^{k+1}}
    $$

    contains (2^k) terms, and each term is at least (1/2^{k+1}). Therefore the whole group is at least

    $$
    2^k \cdot \frac{1}{2^{k+1}} = \frac{1}{2}.
    $$

    So the harmonic series is bounded below by

    $$
    1 + \frac{1}{2} + \frac{1}{2} + \frac{1}{2} + \frac{1}{2} + \cdots
    $$

    which clearly diverges.

    Therefore,

    $$
    \sum_{n=1}^{\infty} \frac{1}{n} = \infty.
    $$

    The moral is: terms going to zero is not enough. The terms must go to zero fast enough.

    One of the first beautiful surprises in analysis is that the harmonic series diverges, even though its terms go to zero.

    The series is

    $$
    1 + \frac{1}{2} + \frac{1}{3} + \frac{1}{4} + \frac{1}{5} + \cdots
    $$

    At first it feels like it should converge, because the terms (1/n) become smaller and smaller. But the condition (a_n \to 0) is necessary for convergence, not sufficient.

    The classic grouping argument is very neat:

    $$
    1 + \frac{1}{2}

    • \left(\frac{1}{3} + \frac{1}{4}\right)
    • \left(\frac{1}{5} + \cdots + \frac{1}{8}\right)
    • \left(\frac{1}{9} + \cdots + \frac{1}{16}\right)
    • \cdots
      $$

    Now look at each group.

    For the group

    $$
    \frac{1}{3} + \frac{1}{4},
    $$

    both terms are at least (1/4), so

    $$
    \frac{1}{3} + \frac{1}{4} \geq \frac{1}{4} + \frac{1}{4} = \frac{1}{2}.
    $$

    For the next group,

    $$
    \frac{1}{5} + \frac{1}{6} + \frac{1}{7} + \frac{1}{8},
    $$

    all four terms are at least (1/8), so

    $$
    \frac{1}{5} + \frac{1}{6} + \frac{1}{7} + \frac{1}{8}
    \geq 4 \cdot \frac{1}{8}
    = \frac{1}{2}.
    $$

    In general, the group

    $$
    \frac{1}{2^k+1} + \frac{1}{2^k+2} + \cdots + \frac{1}{2^{k+1}}
    $$

    contains (2^k) terms, and each term is at least (1/2^{k+1}). Therefore the whole group is at least

    $$
    2^k \cdot \frac{1}{2^{k+1}} = \frac{1}{2}.
    $$

    So the harmonic series is bounded below by

    $$
    1 + \frac{1}{2} + \frac{1}{2} + \frac{1}{2} + \frac{1}{2} + \cdots
    $$

    which clearly diverges.

    Therefore,

    $$
    \sum_{n=1}^{\infty} \frac{1}{n} = \infty.
    $$

    The moral is: terms going to zero is not enough. The terms must go to zero fast enough.

  • RE: 作为生活本身的哲学基础的操练

    三三水这样问我,我认真的思考了一下:你觉得我们应该相信第一印象不

    额我就拿我个人为例吧(?)
    我是一个不看第一印象的人,我的习惯就是不带评价的去观察人(至少是与我不相干不会实际上冒犯到我的人)
    即使我看到一个人,比如你XXXXXX,我也不会下意识的去给人贴标签
    我承认人的多样和复杂这样的客观事实,我承认这些经历会导致一些可能的坏事或者好事
    但是额由于我接触到的可以说是纯坏或者不可理喻而且将这种不可理喻(以一种令我不愉快的方式)施加到我身上的人几乎为零
    大家对我都挺好的,所有我其实潜意识里认为世界上是好人多的(经历导致)
    冒犯到我的人额那就另说了,我对此和希特勒持相同态度()

    我觉得这个是否应该相信第一印象,是一个复杂的命题
    像我的生活环境,是不怎么需要去判断一个人的好坏的,我接触的人也很少,所以我可以不去看第一印象
    但是如果生活动荡,实际上的生活环境接触到的对自己不利的人的可能大的话,应该使用第一印象去进行一些排除

    但是我觉得这个根本的命题可能是:
    我们该如何避开那些潜在的人际威胁(?)
    我们该如何在社交中选择潜在的“好人”(?)
    但是这其实很难,正如我所说,人是很复杂的,就像你,无论你是怎么看待自己的,或者你是如何对待别人,你在对待我(某些特定的人的时候)又是不一样的,是好的

    所以我的结论是,额
    如果自己是一个会被别人以第一印象来评判的人,也就是额第一印象差的人,应该用第一印象去评价别人,因为会造成这样第一印象的环境本身就是不安定的,这时候使用第一印象评价法是可以有效的避开那些风险和威胁的
    如果自己是一个不会被人以第一印象评判的人,那也不用去用第一印象去评价别人,因为你的生活环境既然塑造了这样的你,你接触那些风险和威胁的可能本来就是极小的

    但是说到底,如果一个人带着敌意,隐藏,不可见人的目的与你接触,该被拐去棉被还是得被拐去棉被,和你是否使用第一印象去规避风险没多大关系我感觉

    当然我的社交范围很小啊,这个是前提,如果大家可以在面对冒犯直白的坦言,互相沟通,无法沟通和互相理解就各自保持距离,真心换真心才是最优解吧()保持自我的独立性,不被他人左右(谈何容易()

  • RE: 哈基 项目推荐

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  • RE: 哈基 项目推荐