Quote - You guys do know that you don't really have to aim a mirror, right? It'll reflect anything you put in front of it. What you have to do is position the CAMERA so you can see what is being reflected in the mirror.

 

I think the original question is slightly misworded, and the original poster was really asking for help in achieving, once having set the camera, how to position an object out of view to be seen in the mirror. Which is what the replies have been about, whether it's using trigonometry or in my case D3D's freebie.