# Preliminaries

This appendix contains important ideas about complex numbers, sets, and the logic and techniques of forming proofs. It is not meant to be read straight through, but you should head here when you need to review these ideas.

We choose to expand the set of scalars from the real numbers, $\real{\null}$, to the set of complex numbers, $\complex{\null}$. So basic operations with complex numbers (like addition and division) will be necessary. This can be safely postponed until your arrival in Section O:Orthogonality, and a refresher before Chapter E:Eigenvalues would be a good idea as well.

Sets are extremely important in all of mathematics, but maybe you have not had much exposure to the basic operations. Check out Section SET:Sets. The text will send you here frequently as well. Visit often.