O.1 Identify and classify polygons

Identify and classify polygons

Key Notes:

Polygon

A polygon is a closed figure with straight sides.

Regular polygons

A regular polygon has all equal side lengths and all equal angle measures.

Irregular

If the sides or angles of a polygon are not equal, the polygon is irregular.

Compare these two hexagons. The first one is a regular polygon. It has equal side lengths and equal angles. The second one is not a regular polygon.

🔴Some regular polygons have special names based on their number of sides.

An equilateral triangle is a regular polygon with three sides.

An equilateral triangle is shown. The side lengths are labeled 6. The angles are marked as congruent.

A square is a regular polygon with four sides.

A square is shown. The side lengths are labeled 5. The angles have right angle makers.

But be careful!

Some polygons have equal side lengths or equal angles but not both. These polygons are irregular.

A rhombus has four equal side lengths. It does not necessarily have four equal angles. For example, this rhombus is irregular. It has two obtuse angles and two acute angles.

A rhombus is shown. The side lengths are labeled 4. The rhombus has two obtuse angles and two acute angles.

A rectangle has four equal angles. It does not necessarily have equal side lengths. For example, this rectangle is irregular. It has two sides that are 7 units and two sides that are 3 units.