O = (4, -1)
r = 5 (slider from 1 to 10, step 0.1)
n = 60 (slider from 20 to 200, step 1)
a = 49.7 (slider from 5 to 50, step 0.1)
c = Circle(O, r)
A = Point(c)
L1 = Sequence(Rotate[A, 2.0 * 3.141592653589793 * s / n, O], s, 0.0, n)
L2 = Sequence(Rotate[Element[L1, s + 1.0], 2.0 * 3.141592653589793 * s / a, Element[L1, s]], s, 1.0, n)
Seg1 = Sequence(Segment[Element[L2, s], Element[L2, s + 1.0]], s, 1.0, n - 1.0)
Seg2 = Segment(Element[L2, n], Element[L2, 1.0])
B = Element(L2, floor(n / 2.0))