R = side / (2*sin(pi/n))
(setq denom (sin (quotient pi n)))
(setq denom (times 2.0 denom))
(setq R (quotient side denom))
(setq startAngle (quotient pi n))
(setq angleStep (quotient (times 2.0 pi) n))
(setq pts nil)
(setq i 0)
(while (lessp i n)
(setq theta (plus startAngle (times i angleStep)))
(setq x (plus cx (times R (cos theta))))
(setq y (plus cy (times R (sin theta))))
(setq pts (append pts (list (list x y))))
(setq i (plus i 1))
)