Yahoo Answers is shutting down on May 4th, 2021 (Eastern Time) and beginning April 20th, 2021 (Eastern Time) the Yahoo Answers website will be in read-only mode. There will be no changes to other Yahoo properties or services, or your Yahoo account. You can find more information about the Yahoo Answers shutdown and how to download your data on this help page.

Use the Shell or Disk method (whichever is easier) to compute the volume of the solid?

Use the Shell or Disk method (whichever is easier) to compute the volume of the solid obtained by rotating the region in the figure below about the following. it's from 0 to 1 and the equation of the line is y= x-x^15

I need find the area after rotating about the x and y axis...my T.A. said something about drawing it out and turning the paper to help you use the shell method and disk method when the other would normally be used...but he has a strong accent, and i can't really understand him....thank you

2 Answers

Relevance
  • 1 decade ago
    Favorite Answer

    first

    the area under the curve is

    integral from x = 0 to 1 (written as int_0^1)

    int_0^1 (x-x^15)dx

    Now, to get the volume about the y axis we multiply the area (above) by a differential element

    x dθ and integrate from 0 to 2π

    int_0^2π int_0^1 (x-x^15) x dxdθ

    to get the volume about the x axis we multiply the area (above) by a differential element

    1/2 y dθ and integrate from 0 to 2π

    int_0^2π int_0^1 (x-x^15)*1/2 (x-x^15) dxdθ

    Draw each of the differential elements to see there shape. The shell element looks like rectangle as dx -> 0

    The disk element looks like a piece of pie or a triangle as dx->0. This is where the 1/2 comes from.

  • 5 years ago

    Disk method int x=1 - 5 pi y^2dx = pi 10/x^4 dx -10/3x^3 10/3 ( 1 - 1/5^3)

Still have questions? Get your answers by asking now.