Since Plato laid down his stylus, a lot of work has gone into understanding the properties of 3D shapes, or polyhedra. Perhaps the most celebrated result came from the 18th-century mathematician Leonhard Euler. He noted that every polyhedron has a number of edges that is two fewer than the total of its faces and corners. The cube, for example, has six faces and eight corners, a total of 14, while its edges number 12.
展开▼
