A = (4, 1)
B = (2, 4)
u = Vector(A, B)
C = (6, 2)
D = (7, 4)
v = Vector(C, D)
E = (9, 1)
a = Segment(A, E)
A_1: C
E_1 = (9, 2)
a_1 = Segment(A_1, E_1)
α = Angle(E_1, C, D)
β = Angle(E, A, B)