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Polygons

Interior angles, apothem and area of regular polygons.

A regular n-gon has interior angles of (n − 2)·180°/n. Its area is half the perimeter times the apothem (the distance from the centre to a side), because it splits into n identical triangles.

Worked example: hexagon side 2

Hexagon side 2

6,\ 2

Step by step

  1. \text{interior angle} = \frac{(n-2)\cdot 180^\circ}{n} = 120^\circ

    A regular 6-gon.

  2. P = n s = 12

    Perimeter.

  3. a = \frac{s}{2\tan(\pi/n)} = \sqrt{3} \approx 1.7320

    Apothem (centre to the middle of a side).

  4. A = \tfrac{1}{2} P a = 6 \sqrt{3} \approx 10.392

    Area = half the perimeter times the apothem.

Reveal the answer
A = 6 \sqrt{3} \approx 10.392

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