Find the Fourier series for $$f(x) = \begin{cases} x + 1, \ \ &-1\leq x < 0\\ 1 - x \ \ &0\leq x < 1 \end{cases}$$
I know that the full Fourier series of $\phi(x)$ on $- l < x < l$ is defines as $$\phi(x) = \frac{1}{2}A_0 + \sum_{n=1}^{\infty}A_n\cos\frac{n\pi x}{l} + B_n \sin\frac{n\pi x}{l}$$ But I am not sure how to apply this to $f(x)$. Any help would be appreciated.