matematicas visuales visual math
Resources: Modular Origami
Tetrahedron
The volume of the tetrahedron
The volume of a tetrahedron is one third of the prism that contains it.

Resources: Building polyhedra | modular origami: tetrahedron  | matematicasVisuales
Construcción poliedros| pendientes tetraedros origami | matematicasVisuales
Octahedron and tetrahedron
Volume of an octahedron
The volume of an octahedron is four times the volume of a tetrahedron. It is easy to calculate and then we can get the volume of a tetrahedron.
Resources: Building polyhedra | modular origami: octahedra inside a tetrahedron | matematicasVisuales
Resources: Building polyhedra | modular origami: octahedra inside a tetrahedron | matematicasVisuales
Tetrahedron duality (and its relation with Kepler's Stella Octangula)
The volume of an stellated octahedron (stella octangula)
The stellated octahedron was drawn by Leonardo for Luca Pacioli's book 'De Divina Proportione'. A hundred years later, Kepler named it stella octangula.
A tetrahedron is the dual polyhedron of another tetrahedron | matematicasvisuales
Cuboctahedron
The volume of a cuboctahedron
A cuboctahedron is an Archimedean solid. It can be seen as made by cutting off the corners of a cube.
Resources: Building polyhedra | modular origami: cubocathedron | matematicasVisuales
Resources: Building polyhedra | modular origami: cuboctahedron | matematicasVisuales

Vertices of this beautiful modular origami model, the Omega Star, are vertices of a cuboctahedron:

Volume of a cuboctahedron: Omega Star, modular origami model. Its vertices are the vertices of a cuboctahedron | matematicasvisuales
More

REFERENCES

There are a lot of websites about origami (and videos). One good example is Origami Resource Center.
A reference for the beautiful model of the five tetrahedra inside a dodecahedron: Five Intersecting Tetrahedra (Tomas Hull)

MORE LINKS

Resources: Building Polyhedra with cardboard (Plane Nets)
Using cardboard you can draw plane nets and build polyhedra.
Resources: How to build polyhedra using paper and rubber bands
A very simple technique to build complex and colorful polyhedra.
Resources: Building polyhedra gluing faces
Using cardboard you can build beautiful polyhedra cutting polygons and glue them toghether. This is a very simple and effective technique. You can download several templates. Then print, cut and glue: very easy!
Resources: Building polyhedra gluing discs
Simple technique to build polyhedra gluing discs made of cardboard or paper.
Resources: Acona Biconbi, designed by Bruno Munari
Italian designer Bruno Munari conceived 'Acona Biconbi' as a work of sculpture. It is also a beautiful game to play with colors and shapes.
Resources: Tensegrity
Examples of polyhedra built using tensegrity.
Building polyhedra. Basic techniques: Taller de Talento Matemático de Zaragoza (Spanish)
Material for a session about polyhedra (Zaragoza, 13th Abril 2012).
Construcción de poliedros. Cuboctaedro y dodecaedro rómbico: Taller de Talento Matemático de Zaragoza 2014 (Spanish)
Material for a session about polyhedra (Zaragoza, 9th May 2014). Simple techniques to build polyhedra like the tetrahedron, octahedron, the cuboctahedron and the rhombic dodecahedron. We can build a box that is a rhombic dodecahedron.
Cube, octahedron, tetrahedron and other polyhedra: Taller de Talento Matemático Zaragoza,Spain, 2014-2015 (Spanish)
Material for a session about polyhedra (Zaragoza, 7th November 2014). We study the octahedron and the tetrahedron and their volumes. The truncated octahedron helps us to this task. We build a cubic box with cardboard and an origami tetrahedron.
Duality: cube and octahedron. Taller de Talento Matemático de Zaragoza, Spain. 2015-2016 XII edition (Spanish)
Material for a session about polyhedra (Zaragoza, 23rd Octuber 2015) . Building a cube with cardboard and an origami octahedron.
The Cuboctahedron and the truncated octahedron. Taller de Talento Matemático de Zaragoza, Spain. 2016-2017 XIII edition (Spanish)
Material for a session about polyhedra (Zaragoza, 21st October 2016). Instructions to build several geometric bodies.
Microarquitectura and polyhedra (Spanish)
Microarquitectura is a construction game developed by Sara San Gregorio. You can play and build a lot of structures modelled on polyhedra.
Resources: Building polyhedra using Zome
Examples of polyhedra built using Zome.
The volume of the tetrahedron
The volume of a tetrahedron is one third of the prism that contains it.
Plane developments of geometric bodies: Tetrahedron
The first drawing of a plane net of a regular tetrahedron was published by Dürer in his book 'Underweysung der Messung' ('Four Books of Measurement'), published in 1525 .
Regular dodecahedron
Some properties of this platonic solid and how it is related to the golden ratio. Constructing dodecahedra using different techniques.
Volume of an octahedron
The volume of an octahedron is four times the volume of a tetrahedron. It is easy to calculate and then we can get the volume of a tetrahedron.
Plane developments of geometric bodies (1): Nets of prisms
We study different prisms and we can see how they develop into a plane net. Then we explain how to calculate the lateral surface area.
Plane developments of geometric bodies (3): Cylinders
We study different cylinders and we can see how they develop into a plane. Then we explain how to calculate the lateral surface area.
Plane developments of geometric bodies (5): Pyramid and pyramidal frustrum
Plane net of pyramids and pyramidal frustrum. How to calculate the lateral surface area.
Plane developments of geometric bodies (7): Cone and conical frustrum
Plane developments of cones and conical frustum. How to calculate the lateral surface area.
Plane developments of geometric bodies: Dodecahedron
The first drawing of a plane net of a regular dodecahedron was published by Dürer in his book 'Underweysung der Messung' ('Four Books of Measurement'), published in 1525 .