I am trying to solve the following fourier series: $$f(x) = \begin{cases} \frac{x}{l} &\mbox{if } 0 \leq x \leq l \\ \frac{2l - x}{l} &\mbox{if } l \leq x \leq 2l \\ \end{cases} $$
I know that $\frac{x}{l}$ is an odd function. The one below $2l - x / l$ is neither even/odd. I am not sure how to proceed finding the coefficients