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Change in x and y for a change in position

  1. Jan 18, 2007 #1
    Basically I have a pointer that starts at a particular reference point on a circle with cartisean coordinates,this pointer then moves around the circumference of the circle with an angle theta, the arc length is known but what I need to find is the change relative to x and y.

    I know that the arc length is given by;

    [tex]\delta c =r_{c}\theta_{a}[/tex]

    where [tex]\delta c, r_{c}, \theta_{a}[/tex] are the arc length, radius of the circle and the angle of the arc respectively.

    [tex]\delta c, r_{c}[/tex], and [tex]\theta_{a}[/tex] are known

    but what i don't know is how to find the new position of the pointer relative to x and y;

    hence I need to find the change in x and the change in y.

    I don't really know where to begin so if I could get some pointers rather than the answer then that would great.

    Thanks for your time

    Last edited: Jan 18, 2007
  2. jcsd
  3. Jan 18, 2007 #2
    A point on a circle with radii r could be represent by
    [tex] (rcos\theta ,rsin\theta) [/tex]
    in cartisean coodinate system....
    Now you are asking to find the different of x, and y coordinate when [tex] \theta [/tex] change from [tex] \theta_0 [/tex] to [tex] \theta_1 [/tex]
  4. Jan 18, 2007 #3
    Yes thats what i need to do I think. I attach a crude representation of what I am trying to find

    x and y are the unknowns


    Attached Files:

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