Prove that for any vector A and B the following is true

llAxBll^2 +lA·Bl^2 =llAll^2 llBll^2

2 answers

A×B = |A|*|B|*sinθ
A•B = |A|*|B|*cosθ
now, what is your most basic trig identity?
vector identity :
|A×B| = |A|*|B|*sinθ