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Regular polygons have sides that are all the same length and angles that are all the same size. These polygons are regular:

Regular

The polygons below are not regular. Such polygons are referred to as irregular.

Not Regular

A polygon has line symmetry, or reflection symmetry, if you can fold it in half along a line so the two halves match exactly. The "folding line" is called the line of symmetry.

These polygons have line symmetry. The lines of symmetry are shown as dashed lines. Notice that two of the polygons have more than one line of symmetry.

These polygons do not have line symmetry:

 

 

Each regular polygon has as many lines of symmetry as it has sides.


 

 

Symmetric Figure

A figure that can be folded flat along a line so that the two halves match perfectly is a symmetric figure; such a line is called a line of symmetry.

Examples:

The triangle below is a symmetric figure. The dotted line is the line of symmetry.

The square below is a symmetric figure. It has four different lines of symmetry shown below.

The rectangle below is a symmetric figure. It has two different lines of symmetry shown below.

The regular pentagon below is a symmetric figure. It has five different lines of symmetry shown below.

The circle below is a symmetric figure. Any line that passes through its center is a line of symmetry!

The figures shown below are not symmetric.