Lbraccio: 9
Lst: {-4.5, -3.5, -1.5, 1.5, 3.5, 4.5, 3.5, 1.5, -1.5, -3.5}
vbc: 2
t = 0 (slider from 0 to 20, step 1)
xab: Lst(Mod[t, 10] + 1)
xbc0: 4.5
xbc: xbc0 + (vbc * t)
ybc: 10
B: (xbc, ybc)
A: (xab + xbc, y(B) - Lbraccio)
u = Vector(B, A)