Can a polyhedron be curved? Perhaps this is some kind of mistake? Or maybe this is not a polyhedron? It turns out that there are flexible polyhedra.
To illustrate the usual polyhedron, Alexander uses the icosahedron assembled from our set "Magic Edges"!
Used materials video project "Postnauka" (http://postnauka.ru/).
There are five regular polyhedra: a tetrahedron, an octahedron, a cube (also known as a...