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Homework Help: NEED Help (Basically a Law of Cosines problem)

  1. Feb 4, 2008 #1
    [SOLVED] NEED Help (Basically a Law of Cosines problem)

    So in this problem, all I have to do is to solve it is find out by how much cables AC and AB elongate.

    I thought I could just break it into two Right triangles and just use similar triangles (before and after elongation)

    If you look at the upper right triangle, let's call it ACO, where O denotes the point on the wall halfway between C and B.

    Then I tried doing,

    [tex]\Rightarrow AC'=\frac{300}{300\cos30}*(300\cos30+2)[/tex]

    But this does not work. . . why the hell not??

    My prof gave us the hint: "Use Law of Cosines to find the lengths of AC or AB after elongation"

    How do I use Law of Cos if I don't know the angles after elongation, and moreover what is wrong with the process I tried?

    I hate all of my classes. I miss physics.

  2. jcsd
  3. Feb 4, 2008 #2
    Mechanics of Materials eh?

    http://www.mediafire.com/?0fmwmgeogi6 [Broken]
    Last edited by a moderator: May 3, 2017
  4. Feb 4, 2008 #3
    Where did you get that? Anyway, thanks! I think the dotted line should be labeled [itex]L_{AC}'[/itex] though. But now I see it. I never took a geometry course so this stuff makes me insane.

    Do you know why my original method does not work?
  5. Feb 4, 2008 #4
    because they won't be similar triangles....
  6. Feb 4, 2008 #5
    ummm. . . because the angle changes right?
  7. Feb 4, 2008 #6
  8. Feb 4, 2008 #7
    Short and to the point. I like your style beans :wink:

    Welcome aboard,
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