It can be seen as a 3D extension of the hexagram: the hexagram is a two-dimensional shape formed from two overlapping equilateral triangles, centrally symmetric to each other, and in the same way the stellated octahedron can be formed from two centrally symmetric overlapping tetrahedra.
It is also the least dense of the regular polyhedral compounds, having a density of 2. It is the simplest of five regular polyhedral compounds, and the only regular compound of two tetrahedra. It was depicted in Pacioli's De Divina Proportione, 1509. It is also called the stella octangula (Latin for 'eight-pointed star'), a name given to it by Johannes Kepler in 1609, though it was known to earlier geometers. The stellated octahedron is the only stellation of the octahedron.
Seen as a compound of two regular tetrahedra (red and yellow) This formula applies to any polyhedron that does not have a hole through it.(Redirected from Star Tetrahedron) Stellated octahedron Students can also use their solids to discover Euler's formula for polyhedra: F + V = E + 2, where F represents the total number of faces, V the total number of vertices, and E the total number of edges. For example, Kepler believed the orbits of the planets to be defined by Platonic solids inscribed in one another. People have believed the Platonic solids to have mystical as well as scientific properties. The polygons meet at each vertex in exactly the same way. Archimedean solids have faces that are regular polygons, but the faces don't all have to be the same kind of regular polygon. Make sure the length of the rectangle matches the circumference of the circles. To make a cylinder, use a rectangle with two congruent circles. If you actually have students make templates for all the solids, print them, and then build the solids, this could be a several-day TetrahedronĮxplore More 1. The images below show some samples.Īctivity Time: 50-150 minutes. Try to let students figure out their own templates. It's the same sketch included with the program. Polygons.gsp contains tools for constructing regular polygons. If you have students color the solids and hang them around your classroom, you have wonderful mathematical decorations! Example Sketches: Platonic Templates.gsp contains templates for all the Platonic solids. It is helpful if students can use and access custom tools for regular polygons.
Cube octahedron template pdf how to#
To create the templates, students should understand reflections and rotations and know how to perform them with Sketchpad. Exploring Geometry with The Geometer's Sketchpad © 2002 Key Curriculum PressĬonstructing Templates for the Platonic Solids (page 115) Prerequisites: Students should know the terms polyhedron (polyhedra) and regular polygon. Do some research and make templates for semiregular polyhedra (called Archimedean solids). Make templates for other three-dimensional shapes: cylinders, prisms, and so on. >If you can, print your templates, cut them out, and fold them to see if they work the way you imagined. Describe the method you used to make each template. You can also useĬustom tools for regular polygons to create your templates. Once you've created a regular polygon, you can use reflections and/or rotations to create an adjacent one on your template. Jse Sketchpad to create templates for one or more of the other Platonic solids. An octahedron has eight faces, a dodecahedron has twelve faces, and an icosahedron has twenty faces. The four faces of the tetrahedron are equilateral triangles. As you can see, the cube has six square faces. Each of the solids has more than one possible template. If it doesn't, check the Scale To Fit Page box. Before you print, in the File menu, choose Print Preview. You'll need to mark mirrors (segments) for reflections and to mark centers (points) for rotations. Then you can cut it out and fold it into the Use the Transform menu for reflections and rotations. You can construct a template for an unfolded polyhedron and print it on a piece of stiff paper. A Platonic solid is a polyhedron whose faces are all congruent, regular polygons meeting at each vertex in the same way. After thirteen books of carefully sequenced constructions and theorems, the grand finale of Euclid's Elements is his proof that there are exactly five Platonic solids. That construction was the first proposition in Euclid's Elements.
You've probably constructed an equilateral triangle. Constructing Templates for the Platonic Solids Platonic Templates.gsp
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