A = Point({3, 0})
B = Point({0, 1})
n = Vector((3, 1))
O = Point({0, 0})
u = Vector((-1, 3))
C: (6, 2)
f = Segment(O, C)
P_{0}: (5, 5)
r = Line(C, u)
a = Vector(C, P_{0})
b = Vector(C, O)
α = Angle(a, b)
x_{0} = Point({5, 0})
g = Segment(x_{0}, P_{0})
y_{0} = Point({0, 5})
h = Segment(y_{0}, P_{0})