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Math Help - Arc Length of Curve!

  1. #1
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    Arc Length of Curve!

    What is the arc length of the part of the curve y= (1/12)e^x + (3)e^−x for ln2 ≤ x ≤ ln4?

    I can't seem to get the right answer. I got the derivative of the curve, plugged it into the formula, and still can't get it. Am I missing some trick?

    Thanks!
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  2. #2
    Member anonimnystefy's Avatar
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    Re: Arc Length of Curve!

    hi

    look at this link:Arc length - Wikipedia, the free encyclopedia

    search the part called Finding arc lengths by integrating
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  3. #3
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    Re: Arc Length of Curve!

    I know how to do it. I've done these questions before. But I can't seem to get the answer with this one.
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  4. #4
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    Re: Arc Length of Curve!

    Quote Originally Posted by bhaktir View Post
    What is the arc length of the part of the curve y= (1/12)e^x + (3)e^−x for ln2 ≤ x ≤ ln4?

    I can't seem to get the right answer. I got the derivative of the curve, plugged it into the formula, and still can't get it. Am I missing some trick?

    Thanks!
    note ...

    y' = \frac{e^x}{12} - 3e^{-x}

    (y')^2 = \frac{e^{2x}}{144} - \frac{1}{2} + 9e^{-2x}

    1 + (y')^2 = \frac{e^{2x}}{144} + \frac{1}{2} + 9e^{-2x} = \left(\frac{e^x}{12} + 3e^{-x}\right)^2

    ball is in your court ... finish it.
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