If $f$ is the Fourier series of $g(x) = \begin{cases} 0, & -5 < x < 0 \\ 9x, & 0 \le x < 1 \\ 11, & 1 \le x < 5 \end{cases}$, then
$f(x) = \text{â–¡} + \sum_{n=1}^{\infty} \left[ \text{(â–¡)} \cos \left( \frac{n\pi}{5} x \right) + \text{(â–¡)} \sin \left( \frac{n\pi}{5} x \right) \right]$