Results 1 to 8 of 8
Like Tree1Thanks
  • 1 Post By robbiecee2

Math Help - Differentiating functions

  1. #1
    Newbie
    Joined
    Jul 2012
    From
    milton keynes
    Posts
    10

    Differentiating functions

    I need help understanding how to differentiate functions, i have a few examples below, if you could help me understand that would be great.

    y=3x-5x+1

    p=100- e/6( sorry don't know how to format that correctly)

    r=2ln(t/10)

    the / is me showing it as a fraction, i dont know how to format it correctly
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor

    Joined
    Apr 2005
    Posts
    15,957
    Thanks
    1631

    Re: Differentiating functions

    1) The derivative of af+ bg, where a and b are numbers and f and g are functions, is af'+ bg'. And the derivative of [itex]x^n[/itex], with respect to x, is [itex]nx^{n-}[/itex].

    2) Same as (1). I presume you want to differentiate p with respect to e. And so I am assuming that "e" is NOT the base of the natural logarithm, a constant.

    3) The derivative of ln(u), with respect to u, is 1/u. You also need the "chain rule": if f is a function of u and u is a function of t, df/dx= (df/du)(du/dt). Here, u= t/10.

    Surely these "rules" are in our textbook?
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    May 2011
    Posts
    11
    Thanks
    1

    Re: Differentiating functions

    It's hard to really get the feel for derivatives through text/reading.
    I will be making videos shortly on derivatives, including logarithmic differentiation.
    Please check out my new channel at robbiecee2 - YouTube
    Follow Math Help Forum on Facebook and Google+

  4. #4
    MHF Contributor
    Joined
    Oct 2008
    Posts
    1,035
    Thanks
    49

    Re: Differentiating functions

    Just in case a picture helps anyone, youtubers included! ...



    ... where (key in spoiler) ...

    Spoiler:


    ... is the chain rule. Straight continuous lines differentiate downwards (integrate up) with respect to the main variable (in these cases x or e or t), and the straight dashed line similarly but with respect to the dashed balloon expression (the inner function of the composite which is subject to the chain rule).

    The general drift is...




    _________________________________________

    Don't integrate - balloontegrate!

    Balloon Calculus; standard integrals, derivatives and methods

    Balloon Calculus Drawing with LaTeX and Asymptote!
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Newbie
    Joined
    May 2011
    Posts
    11
    Thanks
    1

    Re: Differentiating functions

    ^^ agreed, good idea.
    Follow Math Help Forum on Facebook and Google+

  6. #6
    MHF Contributor
    Joined
    Oct 2008
    Posts
    1,035
    Thanks
    49

    Re: Differentiating functions

    Thanks. Careful you don't spam though - i.e. link without contributing (appropriately) to the thread.
    Follow Math Help Forum on Facebook and Google+

  7. #7
    Newbie
    Joined
    May 2011
    Posts
    11
    Thanks
    1

    Re: Differentiating functions

    Okay, thanks
    Follow Math Help Forum on Facebook and Google+

  8. #8
    Newbie
    Joined
    Jul 2012
    From
    milton keynes
    Posts
    10

    Re: Differentiating functions

    thanks very much for your help, i am now going to try this with other examples

    Im very new to maths and do not have an A level in it but doing economics at uni so gonna have to get to grips with it, so using summer to help me!
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Differentiating some functions.
    Posted in the Calculus Forum
    Replies: 1
    Last Post: October 17th 2011, 04:07 AM
  2. Differentiating sin functions
    Posted in the Calculus Forum
    Replies: 6
    Last Post: March 27th 2011, 04:16 PM
  3. differentiating log functions
    Posted in the Calculus Forum
    Replies: 1
    Last Post: October 19th 2009, 04:15 PM
  4. differentiating 3 functions
    Posted in the Differential Equations Forum
    Replies: 3
    Last Post: April 15th 2009, 03:12 PM
  5. Differentiating Trignometric Functions
    Posted in the Trigonometry Forum
    Replies: 4
    Last Post: July 19th 2008, 10:37 PM

Search Tags


/mathhelpforum @mathhelpforum