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Math Help - Functions

  1. #1
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    Functions

    For each function f(x) find f'(x)

    A) f(x) = log(1/2) x

    the 1/2 is subscript.

    I got the answer ln(x) / -ln(2).
    Is this correct i don't feel confident in it.
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  2. #2
    Moo
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    Hello,
    Quote Originally Posted by theflyingcow View Post
    For each function f(x) find f'(x)

    A) f(x) = log(1/2) x

    the 1/2 is subscript.

    I got the answer ln(x) / -ln(2).
    Is this correct i don't feel confident in it.
    Not really !
    What you got is another expression for f :

    \log_{1/2}(x)=\frac{\ln(x)}{\ln(1/2)}=-\frac{\ln(x)}{\ln(2)}

    Treat \ln(2) as a constant and then find the derivative !


    MOOOOOOOOOOO
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  3. #3
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    How do I treat it as a constant. What I have is how far I am with keeping up with the teacher
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  4. #4
    Moo
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    Quote Originally Posted by theflyingcow View Post
    How do I treat it as a constant. What I have is how far I am with keeping up with the teacher
    If a is a constant, then the derivative of a \cdot f(x) is a \cdot f'(x)

    So \left(-\frac{\ln(x)}{\ln(2)}\right)'=-\frac{1}{\ln(2)} \left(\ln(x)\right)'

    what's the derivative of the logarithm ?
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  5. #5
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    x / ln10 i believe
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  6. #6
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    wrong mate the derivate of ln (x) is:


    \frac{{d}}{{dx}}ln (x)=\frac{{1}}{{x}}
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  7. #7
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    so where do i go (-1/ln(2)) * (1/x)
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