# Thread: parametric equations(movement around a circle)

1. ## parametric equations(movement around a circle)

So here's the question: Find the parametric equations of a circle with radius 4 and with a center of (3,9) moving counterclockwise around the circle once.

I worked through it and got:

$x= 4cosTheta + 3$

$y= 4sinTheta + 9$

$0

Although I have no idea about the movement around the circle part.

2. Well as $\theta$ goes from $0 \Rightarrow 2\pi$ which direction does it travel normally?

3. I'm pretty sure its Counter clockwise, but if the problem said, for example, it was going clockwise, what would that mean?

4. You are correct, $\theta$ from $0 \Rightarrow 2\pi$ the rotation is counter-clockwise.

In order to go clockwise, you would state something like:

$\theta$ from $2\pi \Rightarrow 0$

5. Originally Posted by eXist
You are correct, from $0 \Rightarrow 2\pi$ the rotation is counter-clockwise.

In order to go clockwise, you would state something like:

$\theta$ from $2\pi \Rightarrow 0$
Would changing the direction change my answer, because I've seen other problems like that and wasn't sure what to do?

6. Originally Posted by rioneye
Would changing the direction change my answer, because I've seen other problems like that and wasn't sure what to do?
Yes, changing your answer would, but you already have it going counter-clockwise. So your answer is correct as it is. I was merely showing you how to reverse the direction if you needed to.

7. Originally Posted by eXist
Yes, changing your answer would, but you already have it going counter-clockwise. So your answer is correct as it is. I was merely showing you how to reverse the direction if you needed to.
ok thank you