C=2πR

C=πd

O = (40.237005351756686, -4.865774281960924)
B = (63.84668588820423, -14.691768493661634)
C = Circle(O, B)
C_1 = Point(C)
a = Line(C_1, O)
D = Intersect(C, a, 2.0)
b = OrthogonalLine(C_1, a)
d_1 = OrthogonalLine(D, a)
e = Segment(C_1, O)
R = Segment(O, D)
f = Distance(b, d_1)
A = Point(b)
E = Point(d_1)
α = Angle(O, C_1, A)
β = Angle(E, D, O)
khoangcachAd = Distance(A, d_1)
c = OrthogonalLine(A, d_1)
F = Intersect(d_1, c)
d = Segment(A, F)