How do I create an equilateral tetrahedron? How to design an equilateral tetrahedron where all edges are of equal length?

Is there any general principle to follow when modelling platonic shapes?
Use the the AddMesh: Extra Objects plugin (to access the user preferences use ctrlaltu):

Now you have to add Mesh-Math Function-Regular Solid

And select Source:Tetrahedron.


For older versions of Blender:
In user preferences  go to &quot;Addons&quot; and enable &quot;Add Mesh:Regular Solids&quot;.

And select platonic solids when pressing shifta