What is a regular polygon?
A polygon is a flat shape with straight sides. A regular polygon has all sides equal and all angles equal. A square is a regular polygon; a normal rectangle is not.
Key idea
Common regular polygons: triangle (3 sides), square (4), pentagon (5), hexagon (6), heptagon (7), octagon (8).
Perimeter = number of sides × length of one side.
Because all the sides of a regular polygon are the same length, we do not have to add each side one by one. We can simply multiply one side by the number of sides. That is why a regular shape is quick to work with.
Worked example
Worked example
A regular hexagon has sides of 5 cm. What is its perimeter?
A hexagon has 6 equal sides.
Perimeter = 6 × 5 = 30 cm.
Check: 30 ÷ 6 = 5 cm per side. Correct.
Remember
- Regular = all sides equal and all angles equal.
- Count sides by the name: penta = 5, hexa = 6, octa = 8.
- Perimeter = number of sides × one side.