# symmetry-triangle-actions.mp4

Chapter section: Discrete symmetries

Caption (verbatim):

A triangle's symmetries

Image description (verbatim):

Triangle symmetry actions

## Before the animation

Chapter lines 40–46:

We can see its obvious symmetry. To categorize its symmetry we can write down all the actions that leave it unchanged:
1. Do nothing
2. Rotate 120°
3. Rotate 240°
4. Flip along an axis
5. Flip then rotate 120°
6. Flip then rotate 240°

## After the animation

Chapter lines 54–54:

We say the triangle "belongs to the $D_3$ symmetry **group**." Any number of objects possess $D_3$ symmetry.