λ = 1 (slider from -5 to 5, step 0.1)
a: λ * x + (1.0 + λ) * y = 2.0
b: (λ + 1.0) * x + (λ - 4.0) * y = λ^(2.0) - 5.0 * λ + 6.0
A = Intersect(a, b)
B = Point(a)
C = Point(b)
α = Angle(B, A, C)