Assertion: octahedron's triangle | /r/HasProperty | each 60 degrees
Facets:
Source sentences:
text: The only other way I can think to describe the 3D shape is like two equilateral triangles (each 60 degrees "out of phase") and with both having 3 triangular sides (so 2*3 sides + 1 top + 1 bottom = 8 faces).