# Rotation angle

1. Sep 28, 2007

### ehrenfest

1. The problem statement, all variables and given/known data
My book says that $$\epsilon \vec{n} \times \vec{q}$$ represents a small rotation about q.
n is an normal vectors
Obviously the cross product is orthogonal to both n and q, but I did not know it corresponded to an angle?
BY the way, how do you make a cross product in tex?
2. Relevant equations

3. The attempt at a solution

Last edited: Sep 28, 2007
2. Sep 28, 2007

### mjsd

cross product in tex? \times will be fine

the epsilon correspond to the small amplitude of your infinitestimal rotation I think

3. Sep 28, 2007

### ehrenfest

But why does this represents an angle?

4. Sep 28, 2007

### Dick

It doesn't represent an angle. It represents an infinitesimal displacement. A small displacement from a vector q rotated around an axis along n should be perpendicular to both. Hence nxq.