We give a mathematical model of chords and use it to talk about musical symmetry.
We describe the symmetries of the English alphabet.
We show that the set of symmetries of any polygon is isomorphic to the set of symmetries of a regular polygon. This is a result attributed to Leonardo da Vinci.
We show that the set of symmetries of an equilateral triangles forms a group under composition.
We determine how regular polygons are symmetrical.