Nonagon area = 20

The of an nonagon is

The area of an nonagon is 20. Calculate side, perimeter

Calculate side:
A = 9/4s2cot(180°/9)
s2 =4A
9cot(180°/9)

s2 =4 x 20
9cot(20)

s2 =80
9 x 2.4

s2 =80
24.

s2 = 3.23529096724
s = √3.23529096724
s = 7

Calculate Perimeter:
P = 9 x side
P = 9 x 7
P = 16.

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 the number of diagonals of the polygon:
Diagonals =n(n - 3)
2

Diagonals =9(9 - 3)
2

Diagonals =9(6)
2

Diagonals =54
2

Diagonals = 27

Calculate the number of diagonals from one vertex:
1 vertex Diagonals = n - 3
1 vertex Diagonals = 9 - 3
1 vertex Diagonals = 6

Calculate the number of triangles that can be drawn from one vertex:
Triangles = N - 2
Triangles = 9 - 2
Triangles = 7