There is a good way to know if a polyhedra is convex. If you place the shape inside a sphere and all of the vertexes were touching the edge of the sphere, then it would be convex. If all of the vertexes didn't touch the edge, then it would be concave. How simply is that?
A simple polygon that is not convex is called concave, non-convex or reentrant. A concave polygon will always have an interior angle with a measure that is greater than 180 degrees.
The opposite of convex is concave. Concave shapes have an inward curve, while convex shapes have an outward curve.
It can be convex or concave.
convex and concave
Lenses: converging (convex) and diverging (concave) Mirrors: concave and convex
concave=in convex=out
convex
A rhombus is an equilateral parallelogram. As such, it is neither concave nor convex.
The Rear view mirrors are convex The Headlights are concave
concave
concave
concave