Question

Let u be an arbitrary fixed unit vector and show that any vector b satisfies

||b||^2 = (u • b)^2 + (u x b)^2

Answer 1

use below :-
|u.b| = | |u||b|cos(theta) |
|uxb| = | |u||b| sin(theta) |

Answer 2

Silly me. Thanks!

Answer 3

np :)

it can get tricky, if we dont remember below :
\((\vec{a})^2 = \vec{a} . \vec{a} = |\vec{a}|^2 \)