Originally Posted by **earboth**

Hello, JakeD,

I only aks to be sure that I did understand all: The angle you described is the one which is build by the two direction vectors. This angle will only be visible for a spectator if he looks along the vector $\displaystyle (2,-3,1)\ \times\ (1,3,2)=(-9,-3,9)=k\cdot (-3,-1,3)$. That's the normal vector of the plane which is build by the two direction vectors.

Looking from any other direction you'll see an angle of different size.

Did I get it now correctly? Quite confusing at all!

Greetings

EB