α = 1.4835298641951802 rad (slider from 0 to 3.141592653589793, step 0.017453292519943295)
A = (2.12, -1.78)
B = (9, -1.8)
a = Segment(A, B)
C = Midpoint(a)
b = OrthogonalLine(C, a)
A' = Rotate(A, 90.0° - α / 2.0, A)
B' = Rotate(B, 90.0° - α / 2.0, A)
a' = Segment(A', B')
c = Line(A, B')
D = Intersect(b, c)
d = Circle(A, D, B)
M_1 = Point(d)
β = Angle(A, M_1, B)
g = CircumcircleArc(B, M_1, A)
M = Point(g)
e = Segment(M, A)
f = Segment(M, B)
γ = Angle(A, M, B)