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Homework Help: Volume of revolution

  1. Jan 23, 2007 #1
    The question I need to solve for an assignment is as follows:
    Find the volume of the solid that is obtained by revolving the region R around the x-axis.

    I figured that the volume would just be the integral of pi R^2 dx, so that would just be pi R^2 x, but that is not the answer. I suspect I am misinterpreting the question.
  2. jcsd
  3. Jan 23, 2007 #2


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    Staff Emeritus
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    Well, R is probably a function of x. If you write the question, as stated, then we'll be more able to help you!
  4. Jan 23, 2007 #3
    My problem is that that is the problem as stated. It doesn't give a function in terms of x.
  5. Jan 23, 2007 #4
    Ah nevermind, I found out that the question was referring to an area already found in a previous question.
  6. Jan 23, 2007 #5

    Gib Z

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    Yes, and if it didn't specify the function, it would be [tex]\pi\int^b_a R^2 dx[/tex] anyway, where R is the closed interval (a,b).
  7. Jan 24, 2007 #6


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    Even that wouldn't make sense! If R is an interval it is not a number! I think both you and ductape are confusing the interval R with "radius" R.
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