- The figurehas no gapsor holes.
- The figureis convex—ithas no indentations.
Example 7
Is a cubea regularpolyhedron?All facesof a cubeare regularpolygons—squares.The cubeis convexbecauseit has no indentedsurfaces.
The cubeis simplebecauseit has no gaps.Therefore,a cubeis a regularpolyhedron.
A polyhedronissemi-regularif all of its facesare regularpolygonsand the samenumberof facesmeetat
everyvertex.
- Semi-regularpolyhedraoftenhavetwo differentkindsof faces,both of whichare regularpolygons.
- Prismswith a regularpolygonbaseare one kind of semi-regularpolyhedron.
- Not all semi-regularpolyhedraare prisms.An exampleof a non-prismis shownbelow.
Completelyirregularpolyhedraalso exist.Theyare madeof differentkindsof regularand irregularpolygons.