You add together the lengths of the nine sides of the nonagon.
nonagon
Because nonagon means 9 sides
Not a regular nonagon.
Add the length of all nine sides up.
Only if all nine sides are the same length.
A nonagon is a 2D shape so you cannot make a 3D nonagon!
A nonagon has nine sides.
Nonagon.
"nonagon" is not a prefix.
A nonagon
A nonagon.