- Decagon (Wikipedia)
In geometry, a decagon (from the Greek δέκα déka and γωνία gonía, “ten angles”) is a ten-sided polygon or 10-gon. The total sum of the interior angles of a simple decagon is 1440°.
- In geometry, a nonagon (/ˈnɒnəɡɒn/) or enneagon (/ˈɛniəɡɒn/) is a nine-sided polygon or 9-gon.
- Octagon (Wikipedia)
In geometry, an octagon (from the Greek ὀκτάγωνον oktágōnon, “eight angles”) is an eight-sided polygon or 8-gon.
