Consider:
\begin{align*}
&\begin{bmatrix} P_1 J&0\\0&NP_2\end{bmatrix}=\\&\begin{bmatrix}I&0\\0&N\end{bmatrix}\begin{bmatrix}P_1&0\\0& P_2\end{bmatrix}
\begin{bmatrix}J&0\\0&I\end{bmatrix}
\stackrel{2.18}{=}\begin{bmatrix}I&0\\0&N\end{bmatrix}[V,W]^{-1}[EV,AW]\begin{bmatrix}
J&0\\0&I\end{bmatrix}\\
&\stackrel{(2.10)}{=}[EV,AW]^{-1}EA[V,W]=[EV,AW]^{-1}AE[V,W]\\
&\stackrel{(2.10)}{=}\begin{bmatrix}J&0\\0&I\end{bmatrix}[V,W]^{-1}[EV,AW]\begin{bmatrix}I&0\\0&N\end{bmatrix}\\
&\stackrel{(2.18)}{=}\begin{bmatrix}J&0\\0&I\end{bmatrix}
\begin{bmatrix}P_1&0\\0&P_2\end{bmatrix}\begin{bmatrix}I&0\\0&N\end{bmatrix}
\begin{bmatrix}JP_1&0\\0&P_2N\end{bmatrix}\\
\end{align*}
The last line should produce an automatic equation numbering, say 2.15. I am using \begin{equation}\end{equation}
, but while I am writing
\begin{align*}
&\begin{bmatrix} P_1 J&0\\0&NP_2\end{bmatrix}=\\&\begin{bmatrix}I&0\\0&N\end{bmatrix}\begin{bmatrix}P_1&0\\0& P_2\end{bmatrix}
\begin{bmatrix}J&0\\0&I\end{bmatrix}
\stackrel{2.18}{=}\begin{bmatrix}I&0\\0&N\end{bmatrix}[V,W]^{-1}[EV,AW]\begin{bmatrix}
J&0\\0&I\end{bmatrix}\\
&\stackrel{(2.10)}{=}[EV,AW]^{-1}EA[V,W]=[EV,AW]^{-1}AE[V,W]\\
&\stackrel{(2.10)}{=}\begin{bmatrix}J&0\\0&I\end{bmatrix}[V,W]^{-1}[EV,AW]\begin{bmatrix}I&0\\0&N\end{bmatrix}\\
\begin{equation}
&\stackrel{(2.18)}{=}\begin{bmatrix}J&0\\0&I\end{bmatrix}
\begin{bmatrix}P_1&0\\0&P_2\end{bmatrix}\begin{bmatrix}I&0\\0&N\end{bmatrix}
\begin{bmatrix}JP_1&0\\0&P_2N\end{bmatrix}\\
\end{equation}
\end{align*}
it is showing some error.
align
, and\nonumber
on the lines that shouldn't be numbered.align*
withalign
(i.e. remove the*
), and then before the\\
of the first few lines, write\nonumber
.align
, notalign*
.