Equality
$$A \neq B$$
A is not equal to B
Subset
$$A \not\subseteq B$$
A is not a subset of or equal to B
Superset
$$A \not\supseteq B$$
A is not a superset of or equal to B
Intersection
$$A \cap B =$$
{ }
Union
$$A \cup B =$$
{ context-free, context-sensitive, creating obstacles, deluding, obscuring knowledge, obscuring perception, recursively enumerable, regular }
Symmetric Difference
$$A \ominus B =$$
{ context-free, context-sensitive, creating obstacles, deluding, obscuring knowledge, obscuring perception, recursively enumerable, regular }
Difference
$$A - B =$$
{ creating obstacles, deluding, obscuring knowledge, obscuring perception }
Difference
$$B - A =$$
{ context-free, context-sensitive, recursively enumerable, regular }
Cartesian Product
$$A \times B =$$
{ (creating obstacles, context-free),
(creating obstacles, context-sensitive),
(creating obstacles, recursively enumerable),
(creating obstacles, regular),
(deluding, context-free),
(deluding, context-sensitive),
(deluding, recursively enumerable),
(deluding, regular),
(obscuring knowledge, context-free),
(obscuring knowledge, context-sensitive),
(obscuring knowledge, recursively enumerable),
(obscuring knowledge, regular),
(obscuring perception, context-free),
(obscuring perception, context-sensitive),
(obscuring perception, recursively enumerable),
(obscuring perception, regular) }