This is either a total newbie question or then it's a totally difficult question. Anyhow.
I'm working on a gravity-simulation program and I'm right now working on a method to define all points within a circle and it seems that I've struck a dead end. I can't think of anything.
I think that analytic geometry holds the key to this, but I haven't figured it out.
So: I don't necessarily need code. I'll just need a method to discern between points inside and outside of a circle whose function and radius are known.