Results 1 to 3 of 3

Math Help - Derivative question

  1. #1
    Junior Member
    Joined
    Sep 2009
    Posts
    34

    Derivative question

    Hi,

    I'm having a little trouble with finding the derivative of this one. The fraction with the square root is giving me the trouble, I'm not sure if I should be using the quotient rule or the chain rule or the chain rule within the quotient rule.
    Anyone able to clarify this for me?

    Thanks
    David

    y=60-\frac{x}{5}+ \frac{\sqrt{100^2+x^2}}{3}
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Senior Member
    Joined
    Jan 2010
    Posts
    354
    Since the denominator of the fraction is a constant, it's easiest to merely factor out the constant. What I mean is:

    \frac{d}{dx} \left[ \frac{\sqrt{100^2+x^2}}{3} \right]= \frac{1}{3} \cdot \frac{d}{dx} \left[ \sqrt{100^2+x^2} \right]

    At this point you should use the chain rule where u=100^2+x^2 to give

    \frac{1}{3} \cdot \frac{d}{du} \left[ u^{1/2} \right] \cdot \frac{d}{dx} \left[100^2+x^2 \right]

    Does this answer your question?
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Junior Member
    Joined
    Sep 2009
    Posts
    34
    Thanks Drumist, it took a but to follow at first but I've got it now. Cheers
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Derivative question
    Posted in the Calculus Forum
    Replies: 1
    Last Post: October 18th 2010, 04:48 PM
  2. [SOLVED] Derivative question Help
    Posted in the Calculus Forum
    Replies: 6
    Last Post: July 14th 2010, 01:52 PM
  3. Replies: 19
    Last Post: October 19th 2009, 06:10 PM
  4. derivative question
    Posted in the Calculus Forum
    Replies: 2
    Last Post: March 24th 2008, 12:31 AM
  5. derivative question
    Posted in the Calculus Forum
    Replies: 1
    Last Post: September 30th 2007, 06:23 PM

Search Tags


/mathhelpforum @mathhelpforum