1 \begin{flalign*}

2     % In this way (this arrange of &), the equation will in the center and align at the third &. If use this method for 'split', equations will not be centered

3     % However, 'flalign' will give each line a separate number. It cannot number the whole equations in one number.

4     && a & = b & \\

5     && a & = b & \\

6     && a & = b & \\

7     && a & = b &

8 \end{flalign*}

\nonumber可以去除编号  或\tag{}修改

\begin{equation*}
\begin{aligned} % requires amsmath; align* for no eq. number
\emph{y}_{\emph{i+1}} & =\emph{terminal}(\emph{y}_{\emph{i}},\alpha(\emph{y}_{\emph{i}},
\emph{l}_{\emph{i+1}})) \\
& =\emph{terminal}(\sigma(\emph{x}_{\emph{i}}),\alpha(\sigma(\emph{x}_{\emph{i}}),
\emph{l}_{\emph{i+1}}))\\
& = \sigma(\emph{next}(\emph{x}_{\emph{i}},\emph{l}_{\emph{i+1}})) = \sigma(\emph{x}_{\emph{i+1}}).
\end{aligned}
\end{equation*}

形如下：

如果公式太长，在长的部分要加上\\如下

\begin{equation}
\begin{aligned}
... = &.......\\
= &.....................................................\\
&............................................................\\
\cong &..................................................................\\
&\emph{sig}\rangle) \mid (\emph{u}',\emph{c}_{u'},\emph{sig})\in\emph{T}\}\cup\{\emph{FS}(\langle RK,\emph{u'},\\
&(\emph{r},\emph{v}_{r}),Enc^{Pub}_{k^{enc}_{\emph{u'}}}(k^{dec}_{\emph{r},\emph{v}_{r}+1},
k^{sig}_{\emph{r},\emph{v}_{r}+1}),\\&Sign^{sig}_{SU}\rangle) \mid (\emph{u'},\emph{c}_{u'},sig) \in
\emph{T} \wedge \emph{u'}\\
=&\\
=&\\
=&
\end{aligned}
\end{equation}