Suppose you want to take a photograph of yourself as you look at your image in a flat mirror 1.8 m away. For what distance should the camera lens be focused? You must be ½ the total distance away: since the angle of incidence is equal to the angle of reflection, the distance needed to get a full view is ½ the total distance. 1.8 / 2 = .9 m seems to easy. Is that right?