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Homework Help: Chain Rule question.

  1. Feb 27, 2015 #1
    1. The problem statement, all variables and given/known data
    y = (tan^-1(6x))^2

    2. Relevant equations
    Chain Rule, power rule?

    3. The attempt at a solution
    Okay, so I did power rule to bring it to 2(tan^-1(6x))
    Then, I know to use the chain rule...
    I get 2(tan^-1(6x)*(1/1+x^2)... I know u = 6x so I play 6 into x^2 and I get 6x^2...
    I see everyone else has gotten 36x^2 on the bottom and I have no idea why, can someone please explain this problem IN DETAIL to me because for all the chain rule problems relevant to one like this, it just skips the algebraic steps which I need to know in this...
  2. jcsd
  3. Feb 27, 2015 #2
    I found out how they got 36x^2, but please a detailed review of this problem would still help!
  4. Feb 27, 2015 #3


    Staff: Mentor

    y' = 2 tan-1(6x) * d/dx(tan-1(6x))

    For that last derivative, imagine that it is d/dx(tan-1(u)). What would that be? You need the chain rule for this derivative.
    Last edited: Feb 27, 2015
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