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Easy but im stuck!

  1. Jan 13, 2009 #1
    hello i am stuck on the following:



    A should equal 2.922 but somehow i cant get it to equal that i have tried using my calc in radians and degrees mode but neither come out with the right answer please help me!
  2. jcsd
  3. Jan 13, 2009 #2


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    The angles are almost certainly in degrees from their size.
    I suspect that you (or the calculator) are doing the sums in the wrong order.
    Write down each term as a number.
    then remember the order:

    ps. Have you copied it down correctly, I get -2.52
    cos(20) is roughly 1 so you have A=k3-(k1+k2) = 3.8-4.8 which is negative
    Last edited: Jan 13, 2009
  4. Jan 13, 2009 #3


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    Are there parentheses in the problem that you didn't include here?
  5. Jan 13, 2009 #4
    hello again well another part of it is that

    B=-2sin(-20) and B=1.826

    which is right you see this equation and the other one are to do with a 4 bar mechanism

    also i have put the correct value -20 for the equations because original the equations are

    theta 2 is -20.
  6. Jan 14, 2009 #5


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    Something doesn't look right. Sin(theta2)=-.913. Therefore theta2 = -66 or -114 (deg.)
  7. Jan 14, 2009 #6
    so sin(theta2) isnt part of the problem -2sin(theta2) is!

    but i understand the -2sin(theta2) its the other equation with cos i dont understand why i dont get the right answer cause i get the right answer for the equation with sin but not the equation with cos.
  8. Jan 15, 2009 #7


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    -2sin(theta2)=1.826. Now divide by -2.
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