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!

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.
    [​IMG]

    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]\frac{AC}{OA}=\frac{AC'}{OA'}[/tex]

    [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.

    Casey
     
  2. jcsd
  3. Feb 4, 2008 #2
  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,
    Casey
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: NEED Help (Basically a Law of Cosines problem)
  1. HELP! Law of Cosines (Replies: 1)

Loading...