Hilbert spaces provide the mathematical foundation for signal
processing theory. In this section we attempt to clearly
define some key Hilbert space concepts like
vectors,
norms,
inner products,
subspaces,
orthogonality,
orthonormal bases, and
projections. The intent is not to bury you
in mathematics, but to familiarize you with the terminology,
provide intuition, and leave you with a "lookup table" for
future reference.