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Math Help - Volume and disk/washer method

  1. #1
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    Volume and disk/washer method

    Hey all,

    Would anyone be able to halp me with this:

    Question:
    Using the disk/washer method, find the volume of the solid by rotating y=x^2+1 and y=3-x^2 region about the x-axis.

    I got pi*(164/15)

    Thanks for the help!! cheers.
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  2. #2
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    Quote Originally Posted by klooless View Post
    Hey all,

    Would anyone be able to halp me with this:

    Question:
    Using the disk/washer method, find the volume of the solid by rotating y=x^2+1 and y=3-x^2 region about the x-axis.

    I got pi*(164/15)

    Thanks for the help!! cheers.
    find points of intersection ...

    x^2+1 = 3-x^2

    x = \pm 1

    washer method integral ...

    V = \pi \int_a^b [R(x)]^2 - [r(x)]^2 \, dx

    using symmetry ...

    V = 2\pi \int_0^1 (3-x^2)^2 - (x^2+1)^2 \, dx = \frac{32\pi}{3}
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  3. #3
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    Thank you much for this guide!

    Cheers!
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