Year 7 Interactive Maths - Second Edition

## Polygons

A polygon is a closed plane figure with three or more sides that are all straight.

Some examples of polygons are shown below.

The following figure is not a polygon as it is not a closed figure.

A circle is not a polygon as it does not have straight sides.

Polygons are named according to the number of sides.  The names of the most common polygons are given below:

### Concave Polygon

If a polygon has a reflex angle, then it is said to be a concave polygon.

An example of concave polygon is shown below.

### Convex Polygon

If a polygon has no reflex angle, then it is said to be a convex polygon.

Examples of the convex polygons are shown below.

### Regular Polygon

A regular polygon's sides are all of the same length and its angles are the same size.

For example, a square is a regular polygon.

Examples of regular polygons are shown below.

### Irregular Polygon

If a polygon is not a regular polygon, then it is said to be an irregular polygon.

For example, the quadrilateral shown below is an irregular polygon.