Editing Polyhedron (section)

=== Flexible polyhedra ===
{{main|Flexible polyhedron}}
It is possible for some polyhedra to change their overall shape, while keeping the shapes of their faces the same, by varying the angles of their edges. A polyhedron that can do this is called a flexible polyhedron. By [[Cauchy's theorem (geometry)|Cauchy's rigidity theorem]], flexible polyhedra must be non-convex. The volume of a flexible polyhedron must remain constant as it flexes; this result is known as the bellows theorem.<ref>{{citation
 | last1 = Demaine | first1 = Erik D. | author1-link = Erik Demaine
 | last2 = O'Rourke | first2 = Joseph | author2-link = Joseph O'Rourke (professor)
 | contribution = 23.2 Flexible polyhedra
 | doi = 10.1017/CBO9780511735172
 | isbn = 978-0-521-85757-4
 | mr = 2354878
 | pages = 345–348
 | publisher = Cambridge University Press, Cambridge
 | title = Geometric Folding Algorithms: Linkages, origami, polyhedra
 | title-link=Geometric Folding Algorithms
 | year = 2007}}.</ref>