Convex vs. Concave Polygons
You may have noticed in all of the polygons recently shown, that sometimes a polygon ‘caves in’ at certain places. This means at least one of the vertices of the polygon is on the inside of the figure.
Take a look at the figure below.
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Concave polygons have at least one vertex which is inside the polygon. |
Do you see that the red vertices are ‘inside’ each polygon? These are called concave polygons.
Another way to look at a concave polygon is that there is at least one interior angle that is greater than 180°.
Let’s look at that same figures and the interior angle that makes it concave.
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Concave polygons have at least one interior angle that is greater than 180 degrees. |
The interior angles are greater than 180°, making these concave polygons.
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If a polygon does not have any vertices ‘inside’ the polygon, which means that all interior angles are less than 180°, the polygon is called convex. |
