P_{0}=(x_{0},y_{0},z_{0})

P(x.y.z)

P_{0} = Point({1, 1, 3})
u = Vector((-1, 2, 1))
r = Line(P_{0}, u)
OP_{0} = Vector(P_{0})
P = Point({-0.5, 4, 4.5})
P_{0}P = Vector(P_{0}, P)
O = Point({0, 0, 0})
OP = Vector(O, P)
Q = Point({0, 3, 4})
v = Vector(P_{0}, Q)