Suppose that
f(x)=\begin{cases}1 − x, & 0\lt x \leq 1, \\0, & 1\lt x \leq 2.\end{cases} (13)
As indicated previously, we can represent f either by a cosine series or by a sine series. Sketch the graph of three periods of the sum of each of these series for −6 ≤ x ≤ 6.