Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Find the slope of the tangent to the curve at the point where x = a

  1. Sep 9, 2008 #1
    1. The problem statement, all variables and given/known data
    http://img214.imageshack.us/img214/4673/mathproblemnw5.png [Broken]

    2. Relevant equations
    lim x->a[tex]\frac{f(a+h)-f(a)}{h}[/tex]

    3. The attempt at a solution
    Ive tried so many times to figure this out. I first substituted the equation into the formula above and multiplied by the conjugate and ended up removing h from the numerator and denominator leaving a -1/2[tex]\sqrt{a}[/tex]. As you can see I have already lost credit for the problem and cannot redo it, but I still want to know how to do it. Any tips and help is appreciated.
    Last edited by a moderator: May 3, 2017
  2. jcsd
  3. Sep 9, 2008 #2


    User Avatar
    Homework Helper

    Um, why can't you just differentiate y directly without using the fundamental definition of the derivative? Why not just apply differentiation rule for powers?
  4. Sep 9, 2008 #3


    User Avatar
    Science Advisor
    Homework Helper

    I would suggest you try writing that as -1/(2*sqrt(a)). I'm really hoping that's what you meant.
  5. Sep 10, 2008 #4

    Gib Z

    User Avatar
    Homework Helper

    It appears from the question type that it is quite possible the OP's course hasn't encountered the power rule yet. And it's still good to know how to do it both ways anyways =]

    Kaleb - You probably just typo-ed, but your posted definition of the derivative is incorrect.
  6. Sep 10, 2008 #5


    User Avatar
    Homework Helper

    If that is true then that is pretty odd. I thought schools always teach the mechanical aspects of calculus before introducing the fundamentals. I learnt it that way.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook