Let the DT siganl be
8 + sin$ ( \frac{2 pi n}{N} ) $ + 8cos$ ( \frac{4 pi n}{N} ) $
= 8 + $ ( \frac{1}{2j}) $ $ { e^(<math>( \frac{j2 pi n}{N} ) $) </math>- e^($ ( \frac{-j2 pi n}{N} ) $ } + 8 { e^($ ( \frac{j4 pi n}{N} ) $) - e^($ ( \frac{-j4 pi n}{N} ) $ }
= 8 + $ ( \frac{-1j}{2}) $ { e^($ ( \frac{j2 pi n}{N} ) $)} + $ ( \frac{1j}{2}) $ { e^($ ( \frac{-j2 pi n}{N} ) $)} +4 { e^($ ( \frac{j4 pi n}{N} ) $)} +4 { e^($ ( \frac{-j4 pi n}{N} ) $)}
Therfore, we have the coefficients as
$ a_0 $ = 8
$ a_1 $ = $ ( \frac{-1 j }{2} ) $
$ a_-1 $ = $ ( \frac{1 j }{2} ) $
$ a_2 $ = 4
$ a_-2 $ = 4
