Assertion: polyhedron's triangle | /r/HasProperty | polygon
Facets:
Source sentences:
text: The familiar triangle and square are both polygons, but polygons can also have more irregular shapes like the one shown on the right.
text: Deltahedra are simply polyhedra whose faces are all equilateral triangles (a polyhedron whose faces are triangles which are not all equilateral is best called an irregular deltahedron).