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Math Help - "Sub" Logarithmic Equations

  1. #1
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    "Sub" Logarithmic Equations

    I have a TI-83 Plus and I don't know how to make, say: "log 1/3" where the "1/3" is sub to the "log".

    Any help?
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  2. #2
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    First off you have to take the log of something, ex.: \log_{\frac{1}{3}}{\color{blue}56}

    As for inputing different logarithmic bases into your calculator, here's a useful property:
    \log_{{\color{blue}a}}{\color{red}b} = \frac{\log_{c} {\color{red}b}}{\log_{c} \color{blue}a} where c can be any number.

    So for your calculator, you'll either be considering c = 10 (denoted just log on the calculator) or c = e (where \ln(x) = \log_{e} (x))

    Example:
    \log_{2}(19) = \frac{\ln(19)}{\ln(2)} = \frac{\log(19)}{\log(2)} (base 10 is implied).
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  3. #3
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    ...so what buttons do I push to put in the sub?
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  4. #4
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    Don't know if you saw my edited post but I posted an example.
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  5. #5
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    Oh, I didn't see that.

    I understand now! Thanks a ton.
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