The exercise
[1, p. 86 ex. 3.16] asks to prove that if the eigenfunctions and eigenvalues of an operator
are
and
, respectively (
) then the eigenfunctions of a function
having an expansion of the form:
will also be
with corresponding eigenvalues
,
. That is
.
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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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