Consider the function $$\phi(x) = \begin{cases} 0 \ \ &-4\leq x < -2,\\ 4 - x^2 \ \ &-2\leq x \leq 2, \\ 0 \ \ &2 < x \leq 4 \end{cases}$$
Defined on the interval $[-4,4]$. Find the Fourier series of $\phi$.
Is this the equation I need to use? $$\phi(x) = \frac{1}{2}A_0 + \sum_{n=1}^{\infty}A_n\cos\frac{n\pi x}{l} + \sum_{n=1}^{\infty} B_n \sin\frac{n\pi x}{l}$$