POL010 · Quadrilaterals & polygons · Classes 6–10
Regular pentagon
A regular pentagon has 5 equal sides and 5 equal angles of 108°. Its diagonals form a star and are in the golden ratio to its sides.
⬠Regular pentagon
📐 Formula
interior 108°; Area ≈ 1.720 s²
✏️ Worked example
Side 4: perimeter 20, interior angle 108°, area ≈ 27.53.
🌍 Where it is used
Shapes of flowers and starfish; the Pentagon building.
❓ Quick check
Sum of the interior angles of a pentagon?
🏋️ Practice
EasyPerimeter of a regular pentagon of side 7?
Answer: 35
MediumDiagonals of a pentagon?
Answer: 5
ChallengeExterior angle of a regular pentagon?
Answer: 72°