O = (1.64, -0.84)
c = Circle(O, 3.5)
A = Point(c)
a = Segment(O, A)
O' = Rotate(O, 20*°, A)
b = Line(A, O')
B_1, B = Intersect(c, b)
d = Segment(O, B)
e = Segment(B, A)
α = Angle(O, A, B)