Yes, -(v × u) = -v × u ?
The length of u × v is |u| |v| sin θ. If u and v are colinear (parallel) what is the length of their cross product?
Since
sin θ = 0
when θ = 0 ,
and the angle between colinear vectors is zero,
the magnitude of the result is zero.
The result is still a vector; it is the
u × u = 0.
Also, since ku is colinear to u (for a scalar k), then:
(ku) × u = 0.
Is the result of u × u perpendicular to both operands?