Decagon Formulas

1. Area of Regular Decagon Formula

Area = 5 \times s 2 \times (1 + \sqrt 5) \times \cot (\frac{π}{10})

Calculated using the side length (s) and cotangent of π/10.

Perimeter = 10 \times s

10 times the side length.

a = \frac{s \times \cot (\frac{π}{10})}{2}

The perpendicular distance from the center to any side.

θ = \frac{180 \times 8}{10}

Each interior angle is 144°.

Exterior Angle = \frac{360}{10}

Each exterior angle is 36°.