Union
$$A \cup B =$$
{ arithmetic, astronomy, fable, fairy-tale, folk-tale, geometry, music, myth, saga }
Symmetric Difference
$$A \ominus B =$$
{ arithmetic, astronomy, fable, fairy-tale, folk-tale, geometry, music, myth, saga }
Difference
$$A - B =$$
{ arithmetic, astronomy, geometry, music }
Difference
$$B - A =$$
{ fable, fairy-tale, folk-tale, myth, saga }
Cartesian Product
$$A \times B =$$
{ (arithmetic, fable),
(arithmetic, fairy-tale),
(arithmetic, folk-tale),
(arithmetic, myth),
(arithmetic, saga),
(astronomy, fable),
(astronomy, fairy-tale),
(astronomy, folk-tale),
(astronomy, myth),
(astronomy, saga),
(geometry, fable),
(geometry, fairy-tale),
(geometry, folk-tale),
(geometry, myth),
(geometry, saga),
(music, fable),
(music, fairy-tale),
(music, folk-tale),
(music, myth),
(music, saga) }
Quadrivium