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Math Help - Finding the surface area of a function

  1. #1
    s3a
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    Finding the surface area of a function

    I successfully did a problem like this before but I am stuck on this one.

    Here is the question:
    Find the area of the surface obtained by rotating the curve
    from to about the -axis.

    Any help would be greatly appreciated!
    Thanks in advance!
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  2. #2
    Super Member General's Avatar
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    Quote Originally Posted by s3a View Post
    I successfully did a problem like this before but I am stuck on this one.

    Here is the question:


    Find the area of the surface obtained by rotating the curve


    from to about the -axis.

    Any help would be greatly appreciated!
    Thanks in advance!
    S = 2 \pi \int_0^4 x \sqrt{1+\left[ y' \right]^2} \, dx ..
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  3. #3
    s3a
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    Instead of x multiplying the square root, shouldn't it be (1+5x^2) multiplying the root?

    Edit: you are right but why? I thought You only put y like that and that if the variables are x you have to put the whole equation in.
    Last edited by s3a; March 25th 2010 at 06:14 PM.
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  4. #4
    Math Engineering Student
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    no because you're rotating about the "y" axis.
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