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Math Help - Surface Area

  1. #1
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    Surface Area

    What is the area of the surface generated wheny=((x^3)/6)+((1)/2x), from x=1, to x=3?
    Last edited by chevy900ss; August 2nd 2009 at 02:08 PM.
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  2. #2
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    You really need to give more information than that. What object are we finding the surface area of?
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  3. #3
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    ok i rewrote the question.
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  4. #4
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    Ok I think you are after the following equation

     SA = 2\pi \int_1^3 f(x) \sqrt{1+[f'(x)]^2} dx

    where f(x) =\frac{x^3}{6}+\frac{1}{2x}

    can you find f'(x) ?
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  5. #5
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    derivative=((x^2)/2)+((1)/-2x^2)
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  6. #6
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    using that equation i get 214pie/9. Is that right?
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  7. #7
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    Quote Originally Posted by chevy900ss View Post
    derivative=((x^2)/2)+((1)/-2x^2)
    Not quite but a good effort.

     f'(x) = \frac{x^2}{2}-\frac{2}{x^2}
    Last edited by pickslides; August 2nd 2009 at 02:56 PM. Reason: typo
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  8. #8
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    how is it -((2)/(x^2). I thought ((1)/2x) is the same as ((x^-1)/2) where you bring the (-1) down front and subtract (1) from the exponent which gives you -((x^-2)/2). Which is -1/2x^2
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  9. #9
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    After a second look you are correct

     f'(x) = \frac{x^2}{2}-\frac{1}{2x^2}

    Sorry about that my friend!
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  10. #10
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    Quote Originally Posted by chevy900ss View Post
    using that equation i get 214pie/9. Is that right?
    Ok is this right using that derivative?
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