“Tetraxis Geometry” was created and produced by Girls' Angle, a math club for girls that meets in Cambridge, Massachusetts.
The mission of Girls' Angle is to foster and nurture girls' interest in mathematics and to help improve K-12 math education.
The mission of Girls' Angle is to foster and nurture girls' interest in mathematics and to help improve K-12 math education.
The shape of the hollow space inside an assembled Tetraxis® toy is called a rhombic dodecahedron.
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The Rhombus in a Rhombic Dodecahedron
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Start with a cube. 
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Look at this red plane inside of the cube.
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These are the dimensions of the rectangle: 
Inscribe a rhombus in the rectangle:
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Put 9 rhombuses together to make one larger rhombus, and add circles at the centers of 4 of the smaller rhombuses.
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You can see that the locations of those circles are the corners of the red rectangle we started with.
If you cut this larger rhombus out of paper, you can then fold it along the dotted lines and tape it together to make the shape of a single Tetraxis® stick. The circles indicate the location of the magnets. |
Click on the image to get a file you can print out.
When folding you have a choice of whether to make the dotted lines be on the inside or the outside of the sticks. If you try it each way, you get two sticks that are mirror images of each another. With 12 of each kind of stick, you can build two paper Tetraxis® puzzles that also are mirror images of each other.
"Tetra" is the Greek numerical prefix that means "four." In the assembled puzzle, sets of three parallel sticks point in one of four different directions.
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