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    1周前 来自 上海

    0
    • $\frac{1}{\pi}=\frac{2\sqrt{2}}{9801}\sum\limits_{k=0}^{\infty}\frac{(4k)!(1103+26390k)}{(k!)^4396^{4k}}\\
      \frac{\pi}{4}=\sum\limits_{k=0}^{\infty}\frac{(-1)^k}{2k+1}\\
      a_0=1,b_0=\frac{1}{\sqrt{2}},t_0=\frac{1}{4},p_0=1\\
      a_{n+1}=\frac{a_n+b_n}{2},b_{n+1}=\sqrt{a_nb_n},t_{n+1}=t_n-p_n(a_n-a_{n+1})^2,p_{n+1}=2p_n\\
      \pi\approx\frac{(a_{n+1}+b_{n+1})^2}{4t_{n+1}}\\
      \Large\pi=\frac{426880\sqrt{10005}}{\sum\limits_{k=0}^{\infty}\frac{(6k)!(545140134k+13591409)}{(3k)!(k!)^3(-640320)^{3k}}}\\
      \normalsize \frac{\pi}{2}=\frac{2}{1}\cdot\frac{2}{3}\cdot\frac{4}{3}\cdot\frac{4}{5}\cdot\frac{6}{5}\cdot\frac{6}{7}\cdots\\
      \arctan{x}=\sum\limits_{k=0}^{\infty}(-1)^k\frac{x^{2k+1}}{2k+1}\\
      \pi=16\arctan{\frac{1}{5}}-4\arctan{\frac{1}{239}}\\
      \pi=24\arctan{\frac{1}{8}}+8\arctan{\frac{1}{57}}+4\arctan{\frac{1}{239}}\\
      \pi=48\arctan{\frac{1}{18}}+32\arctan{\frac{1}{57}}-20\arctan{\frac{1}{239}}\\
      \pi=32\arctan{\frac{1}{10}}-4\arctan{\frac{1}{239}}-16\arctan{\frac{1}{515}}\\
      \pi=\frac{\ln{-1}}{\sqrt{-1}}\\
      \frac{\pi^2}{6}=\sum\limits_{k=1}^{\infty}\frac{1}{k^2}\\
      \huge\pi=3+\frac{1}{7+\frac{1}{15+\frac{1}{1+\frac{1}{292+\frac{1}{1+\cdots}}}}}
      $
      

      1周前 来自 浙江

      0
  • π
    1

    9801
    2
    2

    k=0


    (k!)
    4
    396
    4k

    (4k)!(1103+26390k)

    4
    π

    k=0


    2k+1
    (−1)
    k

    a
    0

    =1,b
    0

    2

    1

    ,t
    0

    4
    1

    ,p
    0

    =1
    a
    n+1

    2
    a
    n

    +b
    n


    ,b
    n+1

    a
    n

    b
    n


    ,t
    n+1

    =t
    n

    −p
    n

    (a
    n

    −a
    n+1

    )
    2
    ,p
    n+1

    =2p
    n

    π≈
    4t
    n+1

    (a
    n+1

    +b
    n+1

    )
    2

    π=
    k=0


    (3k)!(k!)
    3
    (−640320)
    3k

    (6k)!(545140134k+13591409)

    426880
    10005

    2
    π

    1
    2


    3
    2


    3
    4


    5
    4


    5
    6


    7
    6


    arctanx=
    k=0



    (−1)
    k

    2k+1
    x
    2k+1

    π=16arctan
    5
    1

    −4arctan
    239
    1

    π=24arctan
    8
    1

    +8arctan
    57
    1

    +4arctan
    239
    1

    π=48arctan
    18
    1

    +32arctan
    57
    1

    −20arctan
    239
    1

    π=32arctan
    10
    1

    −4arctan
    239
    1

    −16arctan
    515
    1

    π=
    −1

    ln−1

    6
    π
    2

    k=1


    k
    2

    1

    π=3+
    7+
    15+
    1+
    292+
    1+⋯
    1

    1

    1

    1

    1

    4个人觉得很赞

    2026-01-15 来自 浙江

    0
  • 这不会全是你自己推导的吧

    2026-01-04 来自 浙江

    0
  • 连分数是何意味

    2025-12-28 来自 广东

    0
    • 这连分数有个掉规律

      2026-01-10 来自 广东

      0
    • 注意到它用了拉马努金的收敛式(第一行)

      2026-01-10 来自 浙江

      0

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