A:### Quick Answer

A nonagon, or enneagon, is a polygon with nine sides and nine vertices, and it has 27 distinct diagonals. The formula for determining the number of diagonals of an n-sided polygon is n(n - 3)/2; thus, a nonagon has 9(9 - 3)/2 = 9(6)/2 = 54/2 = 27 diagonals.

Know MoreThe diagonal of a polygon is any line segment joining two nonadjacent vertices. A nonagon has nine vertices, and each vertex has six other vertices that are not adjacent; thus, each vertex forms six diagonals. For each vertex, there are three fewer diagonals than there are vertices. This is the first part of the procedure for finding the number of diagonals of a polygon: n(n - 3) = 9 x 6 = 54. Each diagonal has two end points, so in order to not count a duplicate diagonal, the final step is to divide 54 by 2, which results in 27 diagonals.

Learn more about ShapesSources:

- Q:
## What is the name of a nine-sided polygon?

A:A nine-sided polygon is called a nonagon. Another name for a nine-sided polygon is enneagon. The general accepted names are "n-gon" where n is the number of the sides of the polygon.

Full Answer >Filed Under: - Q:
## How many diagonals does a pentagon have?

A:

Full Answer >**A pentagon has five diagonals on the inside of the shape.**The diagonals of any polygon can be calculated using the formula n*(n-3)/2, where "n" is the number of sides. In the case of a pentagon, which "n" will be 5, the formula as expected is equal to 5.Filed Under: - Q:
## How many diagonals does a triangle have?

A:

Full Answer >**A triangle has zero diagonals.**Diagonals must be created across vertices in a polygon, but the vertices must not be adjacent to one another. A triangle has only adjacent vertices.Filed Under: - Q:
## How many diagonals does a dodecagon have?

A:

Full Answer >**A dodecagon, a polygon with 12 sides and 12 vertices, has 54 distinct diagonals.**The formula for determining the number of diagonals of an n-sided polygon is n(n - 3)/2; thus, a dodecagon has 12(12 - 3)/2 = 12(9)/2 = 108/2 = 54 diagonals.Filed Under: