Find the First 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 first 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) $-2+\frac{8}{\pi} \sin x$
B) $2-\frac{4}{\pi} \sin x$
C) $\frac{8}{\pi} \sin x$
D) $\frac{4}{\pi} \sin x$
E) 0