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Derivative Notation

  1. Jun 6, 2006 #1

    danago

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    Gold Member

    Hey. Just a quick simple question. If i have a function such as:
    [tex]
    y = x^2
    [/tex]

    Id write the derivative of function y with respect to x as:
    [tex]
    \frac{{dy}}{{dx}} = 2x
    [/tex]

    What if the function of x was given as:
    [tex]
    f(x) = x^2
    [/tex]

    I know i could write the derivative as f'(x), but how would i write it in the form i used for the first function. Would this be what i should write:
    [tex]
    \frac{{df(x)}}{{dx}}
    [/tex]
    ?

    Would i write:
    [tex]
    \frac{{df}}{{dx}}
    [/tex]
    ?

    Does it even matter? Thanks for the quick advice :cool:

    Dan.
     
  2. jcsd
  3. Jun 6, 2006 #2

    TD

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    Homework Helper

    Both are used: the first one emphasizes the fact that f is a function of x, the second is of course shorter, which is desirable as well sometimes.
     
  4. Jun 6, 2006 #3

    danago

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    Gold Member

    ok thanks :)
     
  5. Jun 6, 2006 #4
    i would write the f(x) on its own following the d/dx fraction, but its just a matter of personal preference to me.
     
  6. Jun 6, 2006 #5

    danago

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    Gold Member

    Like this?
    [tex]
    \frac{d}{{dx}}(x^2 ) = 2x
    [/tex]
     
  7. Jun 6, 2006 #6

    TD

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    Homework Helper

    Yes, this expression is particularly handy when the expression becomes larger.
     
  8. Jun 6, 2006 #7

    danago

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    Gold Member

    ok thanks again :)
     
  9. Jun 6, 2006 #8
  10. Jun 6, 2006 #9

    danago

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    Gold Member

    Oo thanks frog. I had never really seen that last [itex]y_x[/tex] notation.
     
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