You guys have made the mistake of going to School, where they taught you the dreaded Cartesian geometry. This is all much easier if you think in terms of turtle geometry! To draw a circle, you just move a tiny bit, turn a tiny bit, repeat. No trig needed!
(Where'd that formula come from? The circumference of the circle is 2𝜋r, and each step is 1/360th of the circumference. But in practice people don't worry about the exact radius; they just pick a small step length, say 0.5, to get something roughly similar in size to radius-30 circles.)
If you really want to start and end in the center of the circle, that's straightforward too, but a longer script:
