1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

What is the region this question is decribing ?

  1. Jan 27, 2013 #1
    Yeah, so this might sound like a dumb question, but I'm going to ask anyway!

    "Find the volume of the solid generated by revolving the described region about the given axis:

    The region enclosed above by the curve y= 1 + (x^2/4), below by the x-axis, to the left by the y-axis, and to the right by the line x=3, rotated about the y-axis."


    I can easily find the region the question is talking about when it says that it's bound by this or that curve.
    But I'm confused here.

    The curve, y= 1 + x2/4, is above the x-axis.
    So how can we have another boundary that's "below the x-axis" when it also has to be above y= 1 + x2/4??? :confused: ugh.

    And how can the same region be to the left of the y-axis and also to the right of x=3?

    This makes no sense to me. I thought there was supposed to be some region bounded by the curves that gets rotated around the y-axis!

    How do I solve this sort of problem?

    Thanks so much for helping! :)
     
  2. jcsd
  3. Jan 27, 2013 #2

    AlephZero

    User Avatar
    Science Advisor
    Homework Helper

    I think your problem is understanding the English. The sentence splits up like this:

    The region enclosed (bounded) above by the curve y= 1 + (x^2/4),
    and enclosed below by the x-axis,
    and enclosed to the left by the y-axis,
    and enclosed to the right by the line x=3, rotated about the y-axis.

    "Enclosed below by the x axis" means "the x axis is the lower boundary", not "the region is below the x axis".
    "Enclosed to the left by the y-axis" means "the y axis is the left boundary", etc.
     
  4. Jan 27, 2013 #3
    OH, HA! I get it now! I wasn't reading it right! ;) Thanks! :D
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: What is the region this question is decribing ?
  1. Text Region Question (Replies: 1)

Loading...