POL012 · Quadrilaterals & polygons · Classes 7–10
Regular octagon
A regular octagon has 8 equal sides and angles of 135°. It can be made by cutting the corners off a square.
⯃Regular octagon
📐 Formula
Area = 2(1 + √2) s²
✏️ Worked example
Side 3: area ≈ 2 × 2.414 × 9 ≈ 43.46; angle sum 1080°.
🌍 Where it is used
STOP signs, umbrellas, tiles.
❓ Quick check
Interior angle of a regular octagon?
🏋️ Practice
EasyExterior angle of a regular octagon?
Answer: 45°
MediumLines of symmetry?
Answer: 8
ChallengeDiagonals of an octagon?
Answer: 20