More Math Fun
What about
u × 0 ?
The magnitude
|u||0| sin θ
is zero,
and the result is a vector, so:
u × 0 = 0 × u = 0
Now, consider
(ku) × v.
Plug into the formula
for the magnitude,
|u||v| sin θ,
and for the direction
(perpendicular to both operands).