a Highlight your solution, either with a color or a box around it. You are expected to show your work. (1) (2 points) Find the Fourier series, which we denote by $F(x)$, of the function $$ f:(-\pi, o cupo, \pi) \longrightarrow \mathbb{R}, \quad f(x):=\frac{x}{|x|} . $$ Find also the value $F$. (2) (3 points) Find the Fourier sine series, which we denote by $F_{\text {sin }} (x)$, of the function $f(x)=4 x(\pi-x)$ with domain $(0, \pi $. Find also the value of $\sum_{n=1}^{\infty} \frac{(-1)^{n}}{n^{2}}$. CS. SD148