\overrightarrow{v}

\overrightarrow{u}

Q = Point(xAxis)
a = 0.56 (slider from -2 to 2, step 0.005)
L = Point(zAxis)
u = Vector(Q, L)
M: Q + (a * u)
i = Segment(Q, M)
A1: (-8, -6, 2)
A2: (-8, -2, 2)
A2' = Translate(A2, u)
c = Vector(A2, A2')
E = Midpoint(A2, A2')
texte1: "\overrightarrow{QM}=" + (LaTeX[a]) + "\overrightarrow{QL}"