Highly Nonlinear Approximations for Sparse Signal Representation
Orthogonality
Two vectors and
in an inner product space are said to be
orthogonal if
If, in addition,
they are orthonormal.
Two subspaces
and
are orthogonal if
for all
and
.
The sum of two orthogonal subspaces
and
is
termed orthogonal sum and will be indicated as
The subspace
is called the
orthogonal complement of
in
. Equivalently,
is the orthogonal complement of
in
.