Question

This is about vectors.

Answer 1

\(\vec a \) x \(\vec b\) = a*b sin\(\theta\) when they are // the angle between them either 0 or \(\pi\) and sin \(\theta\)=0 . Therefore, when they are// \(\vec a\) x \(\vec b\) =0

Answer 2

axb = ab.sinθ

bxa = ba.sin(-θ) = ab.sin(-θ) = -axb

Answer 3

I'm sorry but I'm a bit confused

Answer 4

assume a is not parallel to b and show that its a contradiction