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Vector question derivative

  1. Oct 9, 2010 #1
    from this photo its a radius multiplied by sinus wich is aproximated to its angle

    and the divided by dt

    32zi49h.gif



    but i dont know how they got the expreesion on the top of the photo

    from the graph on the photo

    11jlsad.jpg
     
  2. jcsd
  3. Oct 10, 2010 #2

    tiny-tim

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    shalom nhrock3! :smile:

    (btw, we say sine or sin, not sinus :wink:)

    |∆r| is approximately the length of the chord, which is 2r |sin(∆θ/2)|, or approximately 2r(|∆θ|/2), = r|∆θ| :wink:

    and the direction of ∆r is obviously tangential, ie along θ

    so ∆r = r(∆θ) θ
     
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