Angle between two vectors [0..2PI]

Hello. I took a look to the FAQs, but I haven’t found the whole solution. I know how to find the angle between two vectors, but not in this range [0…360°] or [0…2PI]. I implement a camera engine…
So, if I well understand :

     Angle = RadianToDegres( acos( |v1 v2| ) )

Where v1 is the Right vector of the camera.
Where v2 is the Right vector of the world (1.0, 0.0, 0.0)

My camera preserve the Right, Up and Forward vector. I want to extract the proper angle of it.

So, pretend the camera rotate 90° around the X axis. Now his UP vector will point forward… So in world coordinate, the camera has an angle of 90° in X axis…

If I add 180° in X axis, the camera has an angle of 270°…

Hope you understand.
Many thanks
Martin Beaudet

I think you need to use matrices.
I have a good matrix class if you want one?

Yes, I’m interested.