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A diagonal is a line between two vertices that is not an edge.

As two vertices are connected by an edge, the number of diagonals from a vertex is the number of vertices (or sides or angles) less 3; as each diagonal is counted twice, once for the vertex at each end of it:

number_of_diagonals = ½ × number_of_vertices × (number_of_vertices - 3)

For a nonagon, it has 9 vertices

→ number_of_diagonals = ½ × 9 × (9 -3) = ½ × 9 × 6 = 27.

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Six. Every n-sided polygon has n(n - 3)/2 sides. It has n vertices, and each of the n vertices has a diagonal with each other vertex, except itself and the two that are adjacent to it; hence, it has n - 3 vertices. But, since each diagonal would be thus counted exactly twice, we must divide the n(n - 3) diagonals thus counted, by two. This formula yields zero, for a triangle; two, for a square or other quadrilateral; five, for a pentagon; and nine, for a hexagon; and so, on.

A nine-sided polygon, or a nonagon, has 27 diagonals.

Q: How many diagonals does a 9 sided polygon have?

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A polygon with n sides has n*(n-3)/2 diagonals. Simple as that. So a 9 sided polygon has 9*6/2 = 27 diagonals.

It depends. It doesn't have to always be the same shape. So it can be 0, it can be 1, as long as it has straight lines and is a closed figure, it's a polygon. * * * * * What? A polygon with n sides has n*(n-3)/2 diagonals. Simple as that. So a 9 sided polygon has 9*6/2 = 27 diagonals.

For a 9 sided polygon it is: 0.5*(92-(3*9)) = 27 diagonals

The formula for the number of diagonals that an N-sided polygon has is# diagonals = N(N-3)/2N(N-3)/29(N-3)/29*(9-3)/29*6/2 = 54/227

A hexagon has 9 diagonals.

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A polygon with n sides has n*(n-3)/2 diagonals. Simple as that. So a 9 sided polygon has 9*6/2 = 27 diagonals.

A 4-sided polygon has 2 diagonals. A 5-sided polygon, 5. 6-sided, 9. By induction, an n-sided polygon has 'n*(n-3)/2' diagonals. "n" is how many sides a shape has. so, (7)*(7-3)/2 now we have, 7*4/2 so, 28/2 = 14 Therefore, a 7-sided polygon would have 14 diagonals.

A regular octadecagon (an eighteen sided polygon) would have nine diagonals.

It depends. It doesn't have to always be the same shape. So it can be 0, it can be 1, as long as it has straight lines and is a closed figure, it's a polygon. * * * * * What? A polygon with n sides has n*(n-3)/2 diagonals. Simple as that. So a 9 sided polygon has 9*6/2 = 27 diagonals.

The formula is: 0.5*(n2-3n) where n is the number of sides of the polygon. So: 0.5*(81-27) = 27 diagonals

For a 9 sided polygon it is: 0.5*(92-(3*9)) = 27 diagonals

Plug 9 as n in this formula: n(n-3)/2

The formula for the number of diagonals that an N-sided polygon has is# diagonals = N(N-3)/2N(N-3)/29(N-3)/29*(9-3)/29*6/2 = 54/227

8+7+6+5+4+3+2+1 = 36 diagonals

A hexagon has 9 diagonals.

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