サイン波合成
\(\displaystyle f(x) = \sum_{k=1}^n \frac{\sin b_k x} {a_k} = \frac{\sin b_1 x}{a_1} + \frac{\sin b_2 x}{a_2} + \dots + \frac{\sin b_n x}{a_n} \)
\( n \) =
\( a_n = b_n = n \)
\( a_n = b_n = 2n - 1 \)
\( a_n = (2n - 1)^2 \times (-1)^{n-1}, b_n = 2n -1 \)