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Confirmation of Method

  1. Dec 7, 2004 #1
    Hello all

    I was just wondering whether this is acceptable:

    f(x) = log (base 5) x.

    f' '(x) = 1 / x * log (base 5) e.

    Any responses are greatly appreciated!
  2. jcsd
  3. Dec 7, 2004 #2


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    Well I don't actually see a method here, try and work it out:

    [tex]y= \log_a (x)[/tex]

    [tex]a^y = x[/tex]

    [tex]\ln (a) a^y \frac{dy}{dx} = 1[/tex]

    [tex]\frac{dy}{dx} = \frac{1}{\ln (a) a^y}[/tex]

    [tex]\frac{dy}{dx} = \frac{1}{\ln (a) a^{\log_a (x)}}[/tex]

    [tex]\frac{dy}{dx} = \frac{1}{\ln (a) x}[/tex]
  4. Dec 8, 2004 #3


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    but ln(5)= 1/ log5(e) so if courtrigrad meant

    [tex]\frac{1}{x log_5(e)}[/tex]

    that's completely correct.
  5. Dec 8, 2004 #4
    I think this is it.

    log(base 5)x=ln(x)/ln(5)

    If not, then I'll hit myself over the head with my Calc book.

    EDIT: I guess somebody pretty much said the same thing before I did... sorry.
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