GeoGebra Classroom

# Rotational symmetry and lines of symmetry of a regular polygon - Lesson+Exploration+Practice

You have learned about rotational symmetry in this activity. Now let's use the rotational symmetry of a regular polygon to explore its lines of symmetry. The lines of symmetry are straight lines that divide a shape into two equal parts, where one part is an exact reflection of the other. Select the number of sides of your polygon, and rotate it. Every time that the rotated polygon overlaps the original one, press the Stamp button on top right, to get a copy of the displayed line stamped in the app. Complete the full rotation of your polygon. You can delete all the lines you stamped by pressing the Erase button displayed below the Stamp one.

Consider your polygon and the lines you have stamped. Are these lines of symmetry for your polygon? Can you relate the number of lines of symmetry of a regular polygon and the number of its sides?

## Food for thought...

Now consider a circle, and the definition of lines of symmetry. How many lines of symmetry does a circle have?