If a straight line from the figure to the mirror intersects the surface of the mirror at an angle of 30 degrees on the left side of the mirror, then a line from the camera to the mirror also needs to be at 30 degrees, but on the right side of the mirror. If the angle between the figure and mirror is 50 degrees then the camera needs to be at 50 degrees, etc. Put another way, the angle which the incident ray makes with the normal (a line perpendicular to the mirror surface) is equal to the angle which the reflected ray makes to the same normal.