Sketch the graph of the periodic function.
Then, find the Fourier coefficients $a_0$, $a_n$, $b_n$ and write out the Fourier series.
6. $f(t) = \begin{cases} 0, & -5 < t < 0 \\ 1, & 0 < t < 5 \end{cases}$
7. $f(t) = \begin{cases} -t, & -\pi < t < 0 \\ 0, & 0 < t < \pi \end{cases}$