It can be convex or concave.
The sum of the exterior angles of ANY polygon, convex or concave, is 360 degrees.
concave
A rhombus is an equilateral parallelogram. As such, it is neither concave nor convex.
Rectangle
convex
The sum of the exterior angles of ANY polygon, convex or concave, is 360 degrees.
concave
concave is inward, convex is outward concave is inward, convex is outward
convex and concave
In 2-d, the naming of polygons is such that a 10 sided shape is a decagon. Even if it is a 5-pointed star shape, it is a decagon. A concave decagon (rather than convex) but still a decagon. In 3-d, a decahedron, possibly, with the term "sides" being used for "faces".
concave concave
The mold for a concave object is convex.The mold for a convex object is concave.
we polish concave and convex with alimunium
Concave
concave=in convex=out
Convex ~
convex