Centering a system of differential equation

Question

I am trying write this system of differential equation, all equation it is a left direction, but I would like to ask how to centering the system in the page.

Thank you very much,

\begin{equation}
\left\{\begin{array}{llll}
\label{eq:siroriginal}
\frac{\mathrm{d} s}{\mathrm{d} t} = \delta -\gamma s-\beta si-sk \\
\frac{\mathrm{d} i}{\mathrm{d} t} = -\gamma i+\beta si-\mu i-ik\\
\frac{\mathrm{d} r}{\mathrm{d} t} = \mu i-rk \\
\end{array}\right.
\end{equation}

Answer 1

Have you tried

\begin{equation}\label{eq:siroriginal}
\left\{\begin{aligned}
\frac{\mathrm{d} s}{\mathrm{d} t} &= \delta -\gamma s-\beta si-sk \\
\frac{\mathrm{d} i}{\mathrm{d} t} &= -\gamma i+\beta si-\mu i-ik\\
\frac{\mathrm{d} r}{\mathrm{d} t} &= \mu i-rk \\
\end{aligned}\right.
\end{equation}

using an appropriate amsmath environment and setting the tabulation markers?

If the problem still persists, try posing the question with a full minimal compilable document in tex.SE