Thank you for you reply. I'm not sure this is homework, because it's actually a very tiny part of a research I'm doing in quantum optics.
I'm aware this is a special case of Fourier series, that's why it is called trigonometric series.
f(x) is a function defined like above, it has no other...
Hi all,
I have a trigonometric function series
$$f(x)={1 \over 2}{\Lambda _0} + \sum\limits_{l = 1}^\infty {{\Lambda _l}\cos \left( {lx} \right)} $$
with the normalization condition
$$\Lambda_0 + 2\sum\limits_{l = 1}^\infty {{\Lambda _l} = 1} $$
and ##\Lambda_l## being monotonic decrescent...