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Homework Help: X= Acos(wt)? X= Asin(wt)?

  1. Oct 18, 2009 #1
    X= Acos(wt)?? X= Asin(wt)??

    1. The problem statement, all variables and given/known data

    X= Acos(wt)??

    X= Asin(wt)??

    Which is right? in some books, x = A sin(wt), while in other books, x= Acos(wt)...

    I'm confused.

    Please explain this to me. Thank you very much.
  2. jcsd
  3. Oct 18, 2009 #2


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    Homework Helper

    Re: X= Acos(wt)?? X= Asin(wt)??

    . f(x) is the projection of a particle moving in a uniform circular motion with radius A and angular velocity ω. If you take the projection on x-axis, then f(x) = Acosωt.
    Ιf you take the projection on y axis, then it is f(x) = Asinωt
  4. Oct 11, 2011 #3
    Re: X= Acos(wt)?? X= Asin(wt)??

    use x=Asin(wt) if the oscillation is starting from the equilibrium position (b/c if u look at a sin curve, it starts at a value of 0), and if it is starting at the amplitude, use x=Acos(wt). (b/c looking at a cosine curve, it starts at the amplitude)

    But since sin and cos are really the same functions except shifted over, these two equations are both true and essentially mean the same thing.
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