A_1 = (0, -2)
B_1 = (10, 8)
a = Line(A_1, B_1)
A = (-10, 6)
B = (-2, 8)
C = (-2, 0)
α = Angle(A, B, C)
b = Segment(A, B)
c = Segment(B, C)
A' = Mirror(A, a)
B' = Mirror(B, a)
d = Segment(A', B')
D'_1 = Mirror(B, a)
C' = Mirror(C, a)
e = Segment(D'_1, C')
β = Angle(C', B', A')