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!

Homework Help: Finding length segment of an ellipse

  1. Mar 27, 2013 #1
    1. The problem statement, all variables and given/known data

    i'm having trouble with these solid of revolution problems because a lot of them require you to find "length of the segment" before evaluating the problem. example:
    a solid lies between planes perpendicular to x=-5 and x=5. the cross section in the xy plane is the ellipse ((x2)/25)+((y2)/36)=1.

    2. Relevant equations
    find L=f(x)

    3. The attempt at a solution
    does that mean i mean i have to make the given equation a function of x? because when i attempt that, it does not turn out to be correct.
    according to the example this is the correct result, L=(12/5)√(25-x2) how can i arrive at that result?

    thank you in advance. by the way, i am posting from my ipad so if the format of the question is not correct, i apologize.
  2. jcsd
  3. Mar 27, 2013 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    I have no idea what you are asking. What does "find L = f(x)" mean? Or "find a length segment"? Volume or surface area might make sense.

    [Edit] Maybe you are asking for the radius of revolution about the x axis? In which case you would solve for y.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted