An octagon has 16 diagonals.
There are 20 diagonals
8 diagonals
4 diagonals
None, if it is an irregular octagon.
20
An octagon has four (4) diagonals, each connecting two opposite vertices.
there are 5, 6, or 7 diagonals in a pentagon
Sides: 8 Diagonals : 20
8
0.5*(82-24) = 20 diagonals
A undecagon has 44 diagonals. A dodecagon has 54 diagonals. An octagon has 20 diagonals. A heptagon has 14 diagonals.