U1_angulo_entre_vectores

a: (4, 1)
b: (1, 3)
c: (-2, 8)
d: (-3, 1)
e: (a * b)
f: (a * c)
g: (a * d)
α = Angle(a, b)
δ = Angle(a, c)
β = Angle(a, d)