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Homework Help: Rotating coordinate system

  1. Jul 17, 2012 #1
    1. The problem statement, all variables and given/known data


    2. Relevant equations

    3. The attempt at a solution

    My question concerns the (1) and (2) next to the figure of the rotating coordinate system.


    So my problem is I can't visualize it. I can visualize that u = ucos(theta) + usin(theta), but I don't get how u = xcos(theta) + ysin(theta).
    If anyone can explain or try to visually show it to me would be great. Thanks.
  2. jcsd
  3. Jul 17, 2012 #2

    Multiply both side of equatlity (1) x=ucos(theta)-vsin(theta) with cos(theta) and both of equality y=ucos(theta).....with sin(theta) you will see some terms will vanish.And you will get your answer...
  4. Jul 17, 2012 #3
    ok i did as you said and got u = sin(theta)y + xcos(theta) which is (2). I still don't get how come u is this quantity. I mean in a visual manner. I'm not so smart to understand it abstractly. Sorry for my poor intelligence.
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