# Spatial vectors

• Jun 19th 2012, 12:07 AM
whyyie
Spatial vectors
Let $\displaystyle \vec{a}$ and $\displaystyle \vec{a}$ be 3d vectors.

Explain in words with the aid of a diagram why:
($\displaystyle \vec{a}$x$\displaystyle \vec{b}$).$\displaystyle \vec{b}$ = 0.

Explain with the aid of a diagram, that if
$\displaystyle \vec{b}$x($\displaystyle \vec{a}$.$\displaystyle \vec{b}$) = $\displaystyle \vec{a}$,
what is $\displaystyle \vec{a}$.$\displaystyle \vec{b}$?

should be using right hand rules etc
• Jun 19th 2012, 04:47 AM
Reckoner
Re: Spatial vectors
Quote:

Originally Posted by whyyie
Explain in words with the aid of a diagram why:
($\displaystyle \vec{a}$x$\displaystyle \vec{b}$).$\displaystyle \vec{b}$ = 0.

Explain with the aid of a diagram, that if
$\displaystyle \vec{b}$x($\displaystyle \vec{a}$.$\displaystyle \vec{b}$) = $\displaystyle \vec{a}$,
what is $\displaystyle \vec{a}$.$\displaystyle \vec{b}$?

These should be easy to answer if you set up a diagram.

What do we know, geometrically, about the cross product of two vectors? And when will the dot product of two vectors be zero?