Upon reflection [computational geometry]

The author looks at the geometry of the classic law of mirror reflection. This law tells us that the angle of incidence equals the angle of reflection. It turns out that this little geometric truth can help solve another set of interesting problems called billiard problems, which describe the shortest path a billiard ball can take on a polygonal table. The author starts by looking at two different derivations of the law of reflection, one geometric and one analytic. He then looks at the problem of finding the shortest circuit of a billiard ball around a triangular table