Centering piece-wise function equation in LibreOffice

Question

I'm sorry if this is off-topic. I am using the TexMaths extension in LibreOffice and I'm attempting to center an equation. However, the equation simply gets displayed and I am unable to alter its horizontal position. So I tried to do this through LaTex but I am unable to get that to work as well. This is what I have so far:

\begin{center}
\[f(x) = \left\{
  \begin{array}{ll}
    sin(x) & : 0 \le x \le 2\pi\\
    -2sin(\dfrac{x}{2}) & : 2\pi < x \le 6\pi\\
    4sin(x + 2\pi) & : 6\pi < x \le 14\pi\\
    sin(x) & : x \ge 14\pi
  \end{array}
\right.
\]
\end{center}

But this still doesn't center it.