90°-70°=20°
Beinchenwinkel

M = (-1.0024555826643047, 1.4076962423812864)
c = Circle(M, 3.0)
A = Point(c)
a = Segment(M, A)
b = OrthogonalLine(A, a)
A' = Rotate(M, 20.0*°, A)
α = Angle(M, A, A')
d = Ray(A, A')
C_1, C = Intersect(c, d)
B' = Rotate(A, 59.99999999999999*°, C)
β = Angle(A, C, B')
e = Ray(C, B')
C_2, B = Intersect(c, e)
Vieleck1, f, e_1, b_1 = Polygon(C_2, A, B)
γ = Angle(C_2, B, A)