B: (3, -2, 1)
A: (2, 1, -1)
u = Vector(B - A)
L = Line(A, u)
D: (11, 3, 1)
v = Vector((4, 2, 1))
M = Line(D, v)
β = Angle(u, v)
a: (4 * x) + (2 * y) + z = 9
C = Intersect(M, a)
f = Segment(C, B)
E = Point(xAxis)
g = Segment(A, C)