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Math Help - another derivative problem

  1. #1
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    another derivative problem

    im lost...
    Attached Thumbnails Attached Thumbnails another derivative problem-8.bmp  
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  2. #2
    Moo
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    Why don't you try a little by yourself ?


    You may know the derivate of a product.

    The derivate of arctan(u(x)) is u'(x)/(1+uČ(x))
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  3. #3
    Senior Member topher0805's Avatar
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    The first thing we have is a product rule. There is also one chain rule. So:

    f'(x) = 6x^3\cdot \frac {1}{1+81x^4}\cdot 18x + 18x^2\arctan {9x^2}

    Then just simplify.
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  4. #4
    Behold, the power of SARDINES!
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    Product rule and chain rule

    f(x)=6x^3 \tan^{-1}(9x^2)

    f'(x)=18x^2 \tan^{-1}(9x^2)+6x^3 \cdot \left( \frac{18x}{1+(9x^2)^2} \right)

    Just simplify from here.

    Good luck.
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