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Know that a regular polygon has sides that are the same length and angles that are the same size

I know that a regular polygon has sides that are the same length and angles that are the same size.

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Year 4

Know that a regular polygon has sides that are the same length and angles that are the same size

I know that a regular polygon has sides that are the same length and angles that are the same size.

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Key learning points

In a regular polygon, the sides are all the same length and the angles are all the same size
In an irregular polygon the sides and angles are not all the same sizes
Irregular polygons can have some angles and sides the same sizes

Keywords

Regular polygon - A polygon where all angles are equal and all side lengths are equal.
Irregular polygon - A polygon where not all angles are equal and / or not all side lengths are equal.
Interior angles - Interior angles are the angles formed inside a polygon by two of its sides.

Common misconception

Many polygons appear regular as all of the sides are the same length. However, it is possible (as the lesson shows) to have polygons which are the same length sides but different interior angles.

Pupils should have previous experience of right angles. Use a right angle 'measurer' to prove that some of the angles in a shape are greater than a right angle and some smaller; as the angles are not all equal, it is not a regular polygon.

If you have access to two-dimensional shapes, it is recommended that you design the lesson to incorporate opportunities to explore the concepts covered using these. Pupils can sort them into polygons / not polygons then take the polygons and re-sort them into regular polygons / not regular polygons.

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This content is © Oak National Academy Limited (2026), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).