Regular octagon split into triangles by its radii

An example figure from the Regular Polygon Generator.

A regular octagon with a dashed radius from its center dot to each of its eight corners, one of them labeled 5 — A regular octagon with a dot at its center and a dashed radius to each of its eight corners, splitting it into eight matching triangles. The radius to the bottom right corner is labeled 5. Use it for central angles, or to find the area from the triangles.

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Answer key

Octagon: 8 sides
Side 3.8, apothem 4.6, radius 5
Each interior angle 135°, central angle 45°
Perimeter 30.6, area 70.7

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