# Finding X,Y points on a Circle

1. Jan 7, 2013

### 777funk

I would like to calculate (X,Y) coords on a circle with a 10" radius.

I have some idea on how this can work but I'm not real solid on it. Say the center is (0,10) and I'd like to solve for Y given an arbitrary X. How would I do this? Obviously (10,0) and (-10,0) and (0,-10) and I know that sin and cos are going to come into it but not sure the actual formula here.

Any help would be greatly appreciated.

EDIT: Thinking a little bit sin()=opp/hyp and cos()=adj/hyp. opposite would be my Y travel and adjacent would be my X. And the radius=10. Theta would be 2*pi/?.

2. Jan 7, 2013

### dydxforsn

It's $x^2 + y^2 = 10^2$. You can do $(x - a)^2 + (y - b)^2 = r^2$ for an arbitrary center point (if the circle is not centered at the origin). In such a case the point (a, b) is your center and 'r' is your radius value.

3. Jan 7, 2013

### 777funk

Ok, thanks. So I WAY over complicated things. Thanks for the help there.

As far as quick easy solving for various points, do you (or anyone else for that matter) have any software recommendations?

Last edited: Jan 7, 2013