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Homework Help: Help with derivatives of natural logs

  1. Oct 15, 2009 #1
    1. The problem statement, all variables and given/known data


    2. Relevant equations

    3. The attempt at a solution
    Honestly I haven't done this in 3 years and a friend asked me to help them with it. I'm at a bit of loss.
  2. jcsd
  3. Oct 15, 2009 #2


    Staff: Mentor

    I'll help you with one of the steps.
    d/dx[ (ln(1+ex))6] = 6(ln(1 + ex)5* d/dx(ln(1 + ex))

    Is that enough of a start?
  4. Oct 15, 2009 #3
    I'll pass it on to her and find out. Thanks.
  5. Oct 15, 2009 #4
    There's a difference between (ln(1+ex))6 and ln(1+ex)6 = ln[(1+ex)6]
    The ln has the exponent, not the argument of the ln, so you can't pull the exponent out in front.
  6. Oct 16, 2009 #5


    Staff: Mentor

    I understand that there is a difference.

    The problem as posted is
    As you can see, it was NOT ln(1 + ex)6, as you seem to think.
    Because the log expression is raised to the 6th power, the derivative is 6( ln(1 + ex))5 * d/dx(ln(1 + ex)).
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