Author: Panagiotis
21
Sep
In exercise
[1, p. 34 exercise 2.2] we are asked to
prove that the rows and columns of a unitary matrix are orthonormal as per
[1, p. 21,(2.21)].
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Author: Panagiotis
21
Sep
In exercise
[1, p. 34 exercise 2.1] we are asked to prove that the inverse of a lower triangular matrix is also lower triangular by using relation
[1, p. 23, (2.30)].
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Author: Panagiotis
13
Jun
In exercise
[1, p. 34 exercise 2.5] we are asked to show that
the matrix

is circulant
when
![\mathbf{e_i}^H=\left[ {\begin{array}{*{20}c}
1 & {e^{-j2\pi f_i } } & {e^{-j2\pi (2f_i) } } & \cdots & {e^{-j2\pi (n - 1)f_i } }
\end{array}} \right], i=1,2](https://lysario.de/wp-content/cache/tex_38ce66bc9234a41f314618cd54d2cfd9.png)
.
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The exercise
[1, p. 34 exercise 2.4] asks to show that if

is a full rank

matrix with

>

,

is a

vector, and

is an

vector, that the effect of the linear transformation
is to project

onto the subspace spanned by the columns of

. Specifically, if

are the columns of

, the exercise
[1, p. 34 exercise 2.4] asks to show that
Furthermore it is asked why the transform

must be idempotent.
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Exercise
[1, p. 14 exercise 1.1] asks to prove that
is a monotonically increasing function over the interval

. Furthermore it asks to show that due to the monotonicity of the peaks of the spectral estimate shown in
[1, Figure 1.2b] that they must also be present in the spectral estimate of
[1, Figure 1.2a].
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