l'angle au centre (α) et l'angle inscrit (β)
interceptent le même arc.
déplacez les points C, D et E

O = Intersect(xAxis, yAxis)
B = Point(xAxis)
c = Circle(O, B)
C = Point(c)
D = Point(c)
E = Point(c)
α = Angle(D, O, C)
β = Angle(D, E, C)
a = Segment(E, C)
b = Segment(E, D)
d = Segment(C, O)
e = Segment(O, D)
f = CircleArc(O, D, C)