O = (0.4, 2.62)
l = Circle(O, 4)
A = Point(l)
B = Point(l)
C = Point(l)
D = Point(l)
q1, a, b, c, d = Polygon(A, B, C, D)
α = Angle(D, A, B)
β = Angle(A, B, C)
γ = Angle(B, C, D)
δ = Angle(A, D, C)