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Math Help - area between this curve

  1. #1
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    area between this curve

    y=e^(-2x) and x+y= 2

    find the volume when rotated over line y=4

    how do you do this?
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  2. #2
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    Quote Originally Posted by akilele View Post
    y=e^(-2x) and x+y= 2

    find the volume when rotated over line y=4

    how do you do this?
    you'll need to use a calculator to find the x-values of intersection of the two graphs.

    let the x-values of the intersection points be x = a and x = b

    use the method of washers ...

    R(x) = 4 - e^{-2x}<br />

    r(x) = 4 - (2-x)


    V = \pi \int_a^b (4 - e^{-2x})^2 - [4 - (2-x)]^2 \, dx
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