Lets assume than $c_n$ is the complex coefficients of the fourier series of $f(x)=2x^3 +x^5 + 5$ in $[-\pi,\pi]$
is it true to argue $$\sum {c_n}=5$$ and the series is absolutely converge?
The only thing I recognize here is that the function is odd. how should I use this? what is the right approach here? should I really calculate $c_n$?