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Homework Help: I cant find theta

  1. May 27, 2010 #1
    http://photoshare.shaw.ca/image/6/8/e/231110/q-0.jpg

    I cant find theta. Anyone help me out here?

    x=theta

    I've tried making Fab=(160cosx)/cos40

    Then plugging it in into the second equation, we get

    160cosxtan40+160sinx-200=0

    160(cosxtan40+sinx)=200

    cosxtan40+sinx=1.25

    Is there a trig identity here? Far as I can get.

    I also tried
    cosx=(Fabcos40)/160
    sinx=200-(Fabsin40)

    Then tanx= [200/(Fabsin40)]-tan40, but no way to eliminate Fab. Or at least I can't.

    Thanks in advance.
     
    Last edited: May 28, 2010
  2. jcsd
  3. May 27, 2010 #2

    kuruman

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    Re: Equilibrium

    Maybe it's just me, but I cannot see an image at the link you provided.
     
  4. May 27, 2010 #3
    Re: Equilibrium

    nope you're right, looks like they took down the image. But fixed!
     
  5. May 27, 2010 #4

    kuruman

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    Re: Equilibrium

    I now see a bunch of equations, but no figure to relate them to.
     
  6. May 27, 2010 #5
    Re: Equilibrium

    Oh, I'm just wondering how to solve theta from those 2 equations. Didn't think a diagram was needed.
     
  7. May 28, 2010 #6

    kuruman

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    Re: Equilibrium

    If the equations are correct, then this is what you do. Solve each equation for the unknown trig function. You will bet

    sinθ = A
    cosθ = B
    where A and B are numbers you can calculate. Divide the top by the bottom to get

    tanθ = A/B. From this get the angle.
     
  8. May 28, 2010 #7
    Re: Equilibrium

    Sorry, I actually put in a divide sign instead of a minus for sinx, not sure how i missed it.

    sinx=200-(Fabsin40)
     
  9. May 28, 2010 #8

    kuruman

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    Re: Equilibrium

    It makes no difference. The method is the same.
     
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