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: 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

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    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

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    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

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    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

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Re: Equilibrium

    It makes no difference. The method is the same.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook