Theorems you might be asked to prove on the midterm:

1. The union of countably many countable sets is countable.

2. The cross-product of two countable sets is countable.

3. Cardinality satisfies the three properties of being an equivalence relation.

4. Be able to prove (using the formal definitions) that a function is one-to-one and onto.

5. The real numbers are uncountable.

6. Limit Laws: If s_n -> s and t_n -> t

a. Then c s_n - > cs

b. Then (s_n + t_n ) -> (s+t)