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Math Help - Solids of Revolution

  1. #1
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    Question Solids of Revolution

    Could use some help on this one:

    To make a doughnut for breakfast, rotate about the y-axis the disk bounded by (x-7)^2 + y^2 = 9 , centered at (7,0). Write a definite integral that gives the volume of your breakfast. Evaluate the integral.

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  2. #2
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    By the Theorem of Pappus, To find the volume of a doughnut generated by revolving the disk of radius r about a line at a distance 'b' units from the center of the disk. The disk has radius 3 and is 7 units from the y-axis.



    V=2{\pi}\int_{-r}^{r}(b-x)(2\sqrt{r^{2}-x^{2}})dx
    Last edited by galactus; December 14th 2007 at 11:39 AM.
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