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Help me with the derivate of this equation?

  1. Jul 15, 2005 #1
    Can sameone help me with the derivate of this equation?

    y=a log10 (x) + B

    Thank you
    Marta
     
  2. jcsd
  3. Jul 15, 2005 #2

    dextercioby

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    What do you mean by "derivate this equation" ?

    Daniel.
     
  4. Jul 15, 2005 #3
    I am supposed to fit some data into this model (y= a log10 (x) + B, where a and b are constants), then I should calculate the slope of the isotherm in order to obtain an index
     
  5. Jul 15, 2005 #4

    dextercioby

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    1.You posted this problem in the wrong forum. The homework one is just above.
    2.The slope is given by the derivative

    [tex] y(x)=a\lg x+b \Rightarrow \frac{dy(x)}{dx}=...? [/tex]

    Daniel.
     
  6. Jul 15, 2005 #5
    I am sorry, I have just realized it...which forum should I go to...general maths or homework?
    But.. do you actually know the derivate of this equation?...
     
  7. Jul 15, 2005 #6
    derivate

    I am supposed to fit some data into this model
    y= a log10 (x) + B, where a and b are constants
    then I should calculate the slope of the isotherm in order to obtain an index

    can someone help me?

    Thank you , marta
     
  8. Jul 15, 2005 #7

    dextercioby

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    What's the connection between the logarithm base 10 and the logarithm base "e" ?

    Daniel.
     
  9. Jul 15, 2005 #8
    I am no mathematician nor student, i just need help to solve this for work purposes and I have no maths books around..the only tool I have is internet.
     
  10. Jul 15, 2005 #9

    dextercioby

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    Well, this is all you need

    [tex] \lg x= \frac{\ln x}{\ln 10} [/tex]

    and now use the derivative of the natural logarithm.

    Daniel.
     
  11. Jul 15, 2005 #10
    i am still struggling!
     
  12. Jul 15, 2005 #11

    dextercioby

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    Well

    [tex] \frac{d}{dx}\left(a\frac{\ln x}{\ln 10}\right)=\frac{a}{\ln 10}\frac{d \ln x}{dx} [/tex]

    Daniel.
     
  13. Jul 15, 2005 #12
    I still haven't figured it out...
    but thank you any way!
     
  14. Jul 15, 2005 #13

    ZapperZ

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    In case you haven't noticed, I've mearged both of your threads into this one. So at some point, the "flow" of the thread may not make any sense.

    :)

    Zz.
     
  15. Jul 15, 2005 #14
    The answer is (for x>0)

    [tex]\frac{a}{ln10} \frac{1}{x}=(\frac{a}{2.302585...} ) \frac{1}{x}[/tex]
     
    Last edited: Jul 15, 2005
  16. Jul 15, 2005 #15
    Thank You!
     
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