Submit
Reset
The number of diagonals increases by 1 when the number of vertices increases by 1.
A dodecagon (12 sides) will have 9 diagonals from any one vertex.
A nonagon (9 sides) will have 9 diagonals from any one vertex.
If you know the number of diagonals from any one vertex in a polygon, you can determine the number of sides that the polygon has.