• Log (base 2) of 3 -- (without a Calculator)

    From HenHanna@21:1/5 to All on Sat Nov 16 19:37:08 2024
    XPost: sci.lang, alt.usage.english

    is there a good way to get this value by hand?

    (without a Calculator) Log (base 2) of 3


    https://www.youtube.com/watch?v=X6C5hGpWW5A

    This clip shows how to derive

    1.5 < Log2(3) < 1.6666666......


    i wonder if there's a way to get better (and better) approximations.

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  • From Daniel@21:1/5 to HenHanna on Mon Nov 18 14:51:15 2024
    XPost: sci.lang, alt.usage.english

    HenHanna <HenHanna@dev.null> writes:

    is there a good way to get this value by hand?

    (without a Calculator) Log (base 2) of 3


    https://www.youtube.com/watch?v=X6C5hGpWW5A

    This clip shows how to derive

    1.5 < Log2(3) < 1.6666666......


    i wonder if there's a way to get better (and better) approximations.

    Is it possibly you can summarize he gist of it in here so we can
    discuss?

    Did you take calculus in college and if so, did you ever learn the limit definition of the derivative?

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  • From HenHanna@21:1/5 to Daniel on Mon Nov 18 20:13:09 2024
    XPost: sci.lang, alt.usage.english

    On Mon, 18 Nov 2024 14:51:15 +0000, Daniel wrote:

    HenHanna <HenHanna@dev.null> writes:

    is there a good way to get this value by hand?

    (without a Calculator) Log (base 2) of 3


    https://www.youtube.com/watch?v=X6C5hGpWW5A

    This clip shows how to derive

    1.5 < Log2(3) < 1.6666666......


    i wonder if there's a way to get better (and better) approximations.

    Is it possibly you can summarize he gist of it in here so we can
    discuss?

    Did you take calculus in college and if so, did you ever learn the limit definition of the derivative?


    i thnk... i knew the Epsilon-Delta def. when i was 13.

    Log2(3) = x

    so 2^x =3 ---------- Square both sides

    2^(2x) = 9 ------ We know that 2^3 = 8

    2^(2x) > 2^3 ---- (2^power is monotonic) (monotonically increasing)

    2x > 3

    x > 1.5


    We get x < 1.6666...... by Cubing both sides


    i wonder if there's a way to get better (and better) approximations.

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  • From Daniel@21:1/5 to HenHanna on Mon Nov 18 22:03:24 2024
    XPost: sci.lang, alt.usage.english, sci.math

    HenHanna <HenHanna@dev.null> writes:

    On Mon, 18 Nov 2024 14:51:15 +0000, Daniel wrote:

    HenHanna <HenHanna@dev.null> writes:

    is there a good way to get this value by hand?

    (without a Calculator) Log (base 2) of 3


    https://www.youtube.com/watch?v=X6C5hGpWW5A

    This clip shows how to derive

    1.5 < Log2(3) < 1.6666666......


    i wonder if there's a way to get better (and better) approximations.

    Is it possibly you can summarize he gist of it in here so we can
    discuss?

    Did you take calculus in college and if so, did you ever learn the limit
    definition of the derivative?


    i thnk... i knew the Epsilon-Delta def. when i was 13.

    Log2(3) = x

    so 2^x =3 ---------- Square both sides

    2^(2x) = 9 ------ We know that 2^3 = 8

    2^(2x) > 2^3 ---- (2^power is monotonic) (monotonically increasing)

    I've been out of college for twenty years and, even though I studied
    math, there's more rust than anything. I see you chose the closest cube
    from 9 to achieve a clean cube root. Which operation did you
    do to get 2x > 3? Did you log both sides? Don't hit me if that's a
    stupid question.

    2x > 3

    x > 1.5


    We get x < 1.6666...... by Cubing both sides

    How do achieve a result of 1.666666 by cubing 1.5? I get 1.5^3 = 3.375.



    i wonder if there's a way to get better (and better) approximations.

    Ever visit sci.math? I'm in there, perhaps we could crosspost this into
    that NG and include them in the conversation. Oh, I will.

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  • From Richard Tobin@21:1/5 to HenHanna@dev.null on Tue Nov 19 19:47:00 2024
    XPost: sci.lang, alt.usage.english

    In article <97e7e6fb078310c8d4d600c247847957@www.novabbs.com>,
    HenHanna <HenHanna@dev.null> wrote:

    i wonder if there's a way to get better (and better) approximations.

    Look for more powers of 2 near to powers of 3.

    For example,

    3^7 (= 2187) > 2^11 (= 2048), so 3 > 2^(11/7), so log2(3) > 11/7 = 1.571+ 3^10 (= 59049) < 2^16 (= 65536), so 3 < 2^(16/10), so log2(3) < 10/6 = 1.6

    3^12 is very close to 2^19, so log2(3) is very close to 19/12 = 1.583+

    -- Richard

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  • From HenHanna@21:1/5 to Richard Tobin on Tue Nov 19 23:08:22 2024
    XPost: sci.lang, alt.usage.english

    On Tue, 19 Nov 2024 19:47:00 +0000, Richard Tobin wrote:

    In article <97e7e6fb078310c8d4d600c247847957@www.novabbs.com>,
    HenHanna <HenHanna@dev.null> wrote:

    i wonder if there's a way to get better (and better) approximations.

    Look for more powers of 2 near to powers of 3.

    For example,

    3^7 (= 2187) > 2^11 (= 2048), so 3 > 2^(11/7), so log2(3) > 11/7 =
    1.571+
    3^10 (= 59049) < 2^16 (= 65536), so 3 < 2^(16/10), so log2(3) < 10/6 =
    1.6

    3^12 is very close to 2^19, so log2(3) is very close to 19/12 = 1.583+

    -- Richard





    Look for more powers of 2 near to powers of 3.

    Thank you.... is there a good way to look for them?


    ___________

    Why didn't i tihnk of that???

    i saw a really nice Clip on Youtube.
    (i think from the 3-Brown 1-Blue guy)

    Plot all points (P cis P) for all prime P

    and the result was Spirals. (amazing graphics effect Zooming out and
    in)


    The spirals resulted from a similar idea (or phenomenon) of
    when multiples of P is close to multiples of 2 Pi.

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  • From HenHanna@21:1/5 to Daniel on Tue Nov 19 23:14:31 2024
    XPost: sci.lang, alt.usage.english

    On Mon, 18 Nov 2024 22:03:24 +0000, Daniel wrote:

    HenHanna <HenHanna@dev.null> writes:

    On Mon, 18 Nov 2024 14:51:15 +0000, Daniel wrote:

    HenHanna <HenHanna@dev.null> writes:

    is there a good way to get this value by hand?

    (without a Calculator) Log (base 2) of 3


    https://www.youtube.com/watch?v=X6C5hGpWW5A

    This clip shows how to derive

    1.5 < Log2(3) < 1.6666666......


    i wonder if there's a way to get better (and better) approximations. >>>
    Is it possibly you can summarize he gist of it in here so we can
    discuss?

    Did you take calculus in college and if so, did you ever learn the limit >>> definition of the derivative?


    i thnk... i knew the Epsilon-Delta def. when i was 13.

    Log2(3) = x

    so 2^x =3 ---------- Square both sides

    2^(2x) = 9 ------ We know that 2^3 = 8

    2^(2x) > 2^3 ---- (2^power is monotonic) (monotonically increasing)

    I've been out of college for twenty years and, even though I studied
    math, there's more rust than anything. I see you chose the closest cube
    from 9 to achieve a clean cube root. Which operation did you
    do to get 2x > 3? Did you log both sides? Don't hit me if that's a
    stupid question.

    2x > 3

    x > 1.5


    We get x < 1.6666...... by Cubing both sides

    How do achieve a result of 1.666666 by cubing 1.5? I get 1.5^3 = 3.375.



    i wonder if there's a way to get better (and better) approximations.

    Ever visit sci.math? I'm in there, perhaps we could crosspost this into
    that NG and include them in the conversation. Oh, I will.


    Thanks.


    so 2^x =3 ---------- Square both sides


    so 2^x =3 ---------- Cubing both sides

    2^(3x) = 27 ------ We know that 2^5 = 32

    ............. we get x < 1.6666......


    ________________ from this NewsReader i can post (max 3 groups)

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  • From Richard Tobin@21:1/5 to jerryfriedman on Wed Nov 20 20:16:30 2024
    XPost: alt.usage.english

    In article <1c945d5b40bb60fb5a27dca42ea9629f@www.novabbs.com>,
    jerryfriedman <jerry.friedman99@gmail.com> wrote:
    Good to see you in a.u.e., Richard!

    Oops! I didn't notice the cross-posting from rec.puzzles.

    And thanks. Perhaps I should look in again.

    -- Richard

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  • From Richard Damon@21:1/5 to Daniel on Fri Nov 22 18:20:39 2024
    XPost: sci.lang, alt.usage.english, sci.math

    On 11/18/24 5:03 PM, Daniel wrote:
    HenHanna <HenHanna@dev.null> writes:

    On Mon, 18 Nov 2024 14:51:15 +0000, Daniel wrote:

    HenHanna <HenHanna@dev.null> writes:

    is there a good way to get this value by hand?

    (without a Calculator) Log (base 2) of 3


    https://www.youtube.com/watch?v=X6C5hGpWW5A

    This clip shows how to derive

    1.5 < Log2(3) < 1.6666666......


    i wonder if there's a way to get better (and better) approximations. >>>
    Is it possibly you can summarize he gist of it in here so we can
    discuss?

    Did you take calculus in college and if so, did you ever learn the limit >>> definition of the derivative?


    i thnk... i knew the Epsilon-Delta def. when i was 13.

    Log2(3) = x

    so 2^x =3 ---------- Square both sides

    2^(2x) = 9 ------ We know that 2^3 = 8

    2^(2x) > 2^3 ---- (2^power is monotonic) (monotonically increasing)

    I've been out of college for twenty years and, even though I studied
    math, there's more rust than anything. I see you chose the closest cube
    from 9 to achieve a clean cube root. Which operation did you
    do to get 2x > 3? Did you log both sides? Don't hit me if that's a
    stupid question.

    2x > 3

    x > 1.5


    We get x < 1.6666...... by Cubing both sides

    How do achieve a result of 1.666666 by cubing 1.5? I get 1.5^3 = 3.375.



    i wonder if there's a way to get better (and better) approximations.

    Ever visit sci.math? I'm in there, perhaps we could crosspost this into
    that NG and include them in the conversation. Oh, I will.


    So, you have 1.5 < log2(3) < 1.666

    Take 2 to the power of each side since that is monotonic

    2^1.5 < 3 < 2^1.666


    For 2^1.5 < 3, square both sides and get 2^3 < 3^2 8 < 9

    for 3 < 2^1.6666 cube both sides, 3^3 < 2^5 27 < 32

    So, we can find the approximations by finding relationships between
    powers of 3 and powers of 2

    If 3^n < 2^m then log2(3) < m/n
    and if 2^m < 3^n then m/n < log2(3)

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  • From David Entwistle@21:1/5 to Richard Tobin on Sat Nov 30 09:18:33 2024
    On Tue, 19 Nov 2024 19:47:00 +0000 (UTC), Richard Tobin wrote:

    In article <97e7e6fb078310c8d4d600c247847957@www.novabbs.com>,
    HenHanna <HenHanna@dev.null> wrote:

    i wonder if there's a way to get better (and better) approximations.

    Look for more powers of 2 near to powers of 3.

    For example,

    3^7 (= 2187) > 2^11 (= 2048), so 3 > 2^(11/7), so log2(3) > 11/7 =
    1.571+
    3^10 (= 59049) < 2^16 (= 65536), so 3 < 2^(16/10), so log2(3) < 10/6 =
    1.6

    3^12 is very close to 2^19, so log2(3) is very close to 19/12 = 1.583+

    -- Richard

    That's a very nice explanation.

    Not a direct answer to HenHanna's original question, but interesting none
    the less. I was trying to work out how Babbage's difference engine, using finite differences, could be used to perform relaterd calculations.I got a
    bit distracted, but the following translation of Briggs' ARITHMETICA LOGARITHMICA was very informative.

    https://www.17centurymaths.com/contents/albriggs.html



    --
    David Entwistle

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