Find the Second Harmonic of the Function $f(x)=$ $\left\{\begin{array}{c}-2 \\2\end{array}\right.$ $\begin{array}{c}-\pi< \\0<\end{array}$

Multiple Choice

Find the second harmonic of the function $f(x) =$$\left\{\begin{array}{c}-2 \\2\end{array}\right.$ $\begin{array}{c}-\pi< \\0<\end{array}$$\begin{array}{l}x \leq 0 \\x \leq \pi\end{array}$ .

A) $-2+\frac{8}{\pi} \sin x+\frac{4}{3 \pi} \sin 3 x$
B) $2-\frac{8}{\pi} \sin x-\frac{4}{3 \pi} \sin 3 x$
C) $\frac{8}{3 \pi} \sin 3 x$
D) $\frac{4}{3 \pi} \sin 3 x$
E) 0