# Change in x and y for a change in position

1. Jan 18, 2007

### NEWO

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;

$$\delta c =r_{c}\theta_{a}$$

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

$$\delta c, r_{c}$$, and $$\theta_{a}$$ 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

N

Last edited: Jan 18, 2007
2. Jan 18, 2007

### chanvincent

A point on a circle with radii r could be represent by
$$(rcos\theta ,rsin\theta)$$
in cartisean coodinate system....
Now you are asking to find the different of x, and y coordinate when $$\theta$$ change from $$\theta_0$$ to $$\theta_1$$

3. Jan 18, 2007

### NEWO

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

thanks

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