Answer

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P = 2
s = 0.22222222222222
A = 0.30527526920715
Interior Angle sum = 1260°
Diagonals = 27
1 vertex Diagonals = 6
Triangles = 7
Sides (Edges) = 9
Faces = 1
Vertices = 9

↓Steps Explained:↓

The Perimeter of a nonagon is 2

Calculate side, area

Calculate side:

s =	P
	9

s =	2
	9

s = 0.22222222222222

Calculate Area:

A = 9/4s²cot(180°/9)

A = 9/4(0.22222222222222)²cot(20)

A = 9/4(0.049382716049383)cot(20)

A = 0.11111111111111 x 2.7474774228644

A = 0.30527526920715

Calculate Sum of the Interior Angles:

Interior Angle Sum = (sides - 2) x 180°

Interior Angle Sum = (9 - 2) x 180°

Interior Angle Sum = 7 x 180°

Interior Angle sum = 1260°

Calculate polygon diagonals

Diagonals =	n(n - 3)
	2

Diagonals =	9(9 - 3)
	2

Diagonals =	9(6)
	2

Diagonals =	54
	2

Diagonals = 27

Calculate 1 vertex diagonals:

1 vertex Diagonals = n - 3

1 vertex Diagonals = 9 - 3

1 vertex Diagonals = 6

Calculate triangles from one vertex:

Triangles = N - 2

Triangles = 9 - 2

Triangles = 7

Other Properties:

Sides (Edges) = 9

Faces = 1

Vertices = 9

Final Answers