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Question about calculating area and volume

  1. Dec 20, 2011 #1
    When calculating the volume of say y = x^3 rotated around the y axis from -2<=x<=2 I am the calculating a space occupied by a 3D figure... but when Im calculating the area between say y = x^3 and y=(-x)^3 from 0<= y <=8 what exactly is this area? is it surface area???
     
  2. jcsd
  3. Dec 21, 2011 #2

    NascentOxygen

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    Staff: Mentor

    It's the sum of the areas of all those whisker-thin rectangles, each of height equal to the vertical distance between the curves, viz, x^3 - (-x)^3, and of horizontal width equal to dx or Δx. So it's an area on the x-y plane, a flat area. You could call it a surface area, if you wish, but then all areas could be considered surface areas. couldn't they?
     
  4. Dec 21, 2011 #3

    HallsofIvy

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    No, there is no "surface" are because this is not a three dimensional problem. It is simply area in the xy-plane.
     
  5. Dec 21, 2011 #4
    I guess ill figure out the importance of calculating area later because right now I dont see it..
     
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