1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

How to solve this logarithmic function?

  1. Nov 20, 2012 #1
    How do I find the derivative of (x)=ln(x+(x^2-1)1/2)

    The answer is suppose to be 1/(x2-1). But I keep ending up with 2x/(x2-1).
     
    Last edited: Nov 20, 2012
  2. jcsd
  3. Nov 20, 2012 #2

    Mark44

    Staff: Mentor

    Is this supposed to be f(x) = ...
    Show us what you did.

    Also, do not delete the three parts of the homework template. They are there for a reason.
     
  4. Nov 20, 2012 #3
    Well, the problem says h(x).


    (d/dx)ln(x+(x2-1)1/2*(d/dx)(x+(x2-1)1/2*(d/dx)(x2-1)1/2*(d/dx)(x2-1).

    1/(x+(x2-1)1/2 * 1+[x/(x2-1)]1/2 * x/(x2-1)1/2 * 2x

    Which actually gets me 2x2/(x2-1)
     
  5. Nov 20, 2012 #4

    haruspex

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    I can't decipher that line. Left and right parentheses don't match up. Is there an equals sign missing? If not, I don't understand why there are any log terms in there.
     
  6. Nov 20, 2012 #5

    Mark44

    Staff: Mentor

    How was I to tell? You wrote this
    There are actually too many "d/dx" operators in there, although I get what you're trying to do. Your task is to do this differentiation:

    d/dx(ln(x+(x2-1)1/2)

    $$= \frac{1}{x + (x^2 - 1)^{1/2}} \cdot d/dx(x + (x^2 - 1)^{1/2})$$
    $$= \frac{1}{x + (x^2 - 1)^{1/2}} \cdot (1 + d/dx[(x^2 - 1)^{1/2}]$$
    and so on, whittling away at it a little at a time.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: How to solve this logarithmic function?
  1. Logarithmic Functions (Replies: 3)

  2. Logarithmic Function (Replies: 4)

Loading...