1. Not finding help here? Sign up for a free 30min 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!

Calc 2 solids of revolution help

  1. Sep 2, 2013 #1
    A solid lies between planes perpendicular to the x-axis at x=-a and x=a for values of a>0 to be given below in parts (i) and (ii). In each case the cross-sections perpendicular to the x-axis between these planes run from the semicircle y=√(a^2-x^2) to the semicircle
    y=-√(a^2-x^2).

    If a=7 and the cross-sections are equilateral triangles with bases in the x-y plane, find a formula for the area A(x) of the cross-section at location x.


    For the base i used 2*√(a^2-x^2), for the height i used √(a^2-x^2)/tan(30). so i get
    (a^2-x^2)/tan(30) as an answer, which is not right. what am i doing wrong i cant seem to figure it out.

    i uploaded a picture of what the problem gave me if it helps.
    THANKS!!!
     

    Attached Files:

    • 6.1d.pdf
      6.1d.pdf
      File size:
      253.3 KB
      Views:
      46
    Last edited: Sep 2, 2013
  2. jcsd
  3. Sep 2, 2013 #2
    Why do you think that is not right?
     
  4. Sep 2, 2013 #3
    its a problem on my online homework and when i type in that answer it says its wrong
     
  5. Sep 3, 2013 #4

    verty

    User Avatar
    Homework Helper

    You made a mistake finding the height of the triangle.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted