O = (-0.9, 2.6)
r = 2 (slider from 0 to 5, step 0.1)
c = Circle(O, r)
A = Point(c)
B = Point(c)
a = Segment(A, B)
d = CircleArc(O, B, A)
b = Segment(A, O)
e = Segment(O, B)
α = Angle(B, O, A)
C_1 = Midpoint(A, B)
f = Ray(O, C_1)
C_2 = Midpoint(A, B)
g = Ray(O, C_2)
C = Intersect(c, g)