📁 皮奥尔伊赫埃迪尔阿
A polyhedron is a three-dimensional solid composed of a set of polygons connected at their edges. All of the faces of a polyhedron are flat, as opposed to spheres and cones, which have round surfaces. Polyhedra can be regular; a regular polyhedron is one composed of regular polygons (polygons where all sides and angles are the same). There are nine regular polyhedra - five convex and five concave. The five convex polyhedra are the cube, tetrahedron, octahedron, dodecahedron, and icosahedron. These five shapes are sometimes referred to as Platonic solids. Polyhedra composed of two different types of regular polygons are called semiregular polyhedra or Archimedean solids, of which there are thirteen.
条目 (20+)
Projections of Complex Algebraic Curves to Real 3-space
http://math.byu.edu/~jarvis/banks-stuff.html
Sangaku: Reflections on the Phenomenon
http://www.cut-the-knot.org/pythagoras/Sangaku.shtml
Archimedes' Book of Lemmas
http://www.cut-the-knot.org/Curriculum/Geometry/BookOfLemmas/index.shtml
NPR : Mathematicians Get Crafty with Geometry
http://www.npr.org/templates/story/story.php?storyId=4531695
Geometry and the Imagination in Minneapolis
http://www.geom.uiuc.edu/docs/doyle/mpls/handouts/handouts.html
Encyclopedia of Triangle Centers
http://faculty.evansville.edu/ck6/encyclopedia/ETC.html