Shadows: A sphere might cast a circular shadow, but more typical the sphere's shadow is a cone in space and thus casts an elliptical shadow!

We considered how the tetrahedron might case shadows. Sometimes a triangle, sometimes a quadrilateral.

The assignment: shadows for the frame of a cube.

Show video on symmetries from FAPP.

there are seven possible distinct types of frieze or

translation |
horizontal |
vertical |

reflection + |
glide |
rotation |
reflection + |

translations |
reflections |
reflections + |

glide |
reflections + |
rotations (2) |

reflections + |
rotations (2) + |
rotations (2) + |

rotations (4) |
reflections + |
rotations (4) + |

rotations (3) |
reflections + |
rotations (3) + |

rotations (6) |
reflections + |