Nonagon Formulas

1. Area of Regular Nonagon Formula

Area = 9 \times s 2 \times (1 + \sqrt 5) \times \cot (\frac{π}{9})

The area uses the side length (s) and cotangent of π/9.

Perimeter = 9 \times s

The perimeter is 9 times the side length (s).

a = \frac{s \times \cot (\frac{π}{9})}{2}

The apothem is the perpendicular distance from the center to a side midpoint.

θ = \frac{180 \times 7}{9}

Each interior angle is 140°.

Exterior Angle = \frac{360}{9}

Each exterior angle is 40°.