# Equation number doesn't appear when the equation comes in 2 different page

I have a long equation which I break to lines by using either align or split. Unfortunately in my pdf file, half of this equation comes in one page and rest is in the next page and that is the reason, the equation number does not appear though the order of equation is preserved. Also, I can't refer to this equation though it has a label. How can I have the equation number after the equation? Note that I have to use \scriptstyle to make the equation fit on page width.

Here is a smaller example:

\documentclass{article}

\usepackage{amsmath}

\begin{document}
{\scriptstyle
\label{Model} \begin{align} \prod_{i=1}^{n}&\Biggl\{\Big[\sum_{k=1}^{2}\left(\frac{1}{\nu (\sum_{j=1}^{t-1}\exp(\rho(j)+\beta^TZ_i))+1}\right)^{1/\nu}-\left(\frac{1}{\nu (\sum_{j=1}^{t}\exp(\rho(j)+\beta^TZ_i))+1}\right)^{1/\nu}\pi_{\eta}^{(k)}(\varepsilon_i)\Big]^{1-\delta_i} \times \notag \\ &\Biggl[\left(\left(\frac{1}{\nu (\sum_{j=1}^{t-1}\exp(\rho(j)+\beta^TZ_i))+1}\right)^{1/\nu}-\left(\frac{1}{\nu (\sum_{j=1}^{t}\exp(\rho(j)+\beta^TZ_i))+1}\right)^{1/\nu}\pi_{\eta}^{(1)}(\varepsilon_i)\right)^{I_{(\varepsilon_i_i=1)}} \times \notag \\ &\left(\left(\frac{1}{\nu (\sum_{j=1}^{t-1}\exp(\rho(j)+\beta^TZ_i))+1}\right)^{1/\nu}-\left(\frac{1}{\nu (\sum_{j=1}^{t}\exp(\rho(j)+\beta^TZ_i))+1}\right)^{1/\nu}\pi_{\eta}^{(2)}(\varepsilon_i)\right)^{I_{(\varepsilon_i_i=2)}}\Biggr]^{\delta_i}.p_i\Biggr\}^{W_i\xi_i} \times \notag\\ &\Biggl\{\Big[\sum_{k=1}^{2}\left(\frac{1}{\nu (\sum_{j=1}^{t-1}\exp(\rho(j)+\phi^TZ_i))+1}\right)^{1/\nu}-\left(\frac{1}{\nu (\sum_{j=1}^{t}\exp(\rho(j)+\phi^TZ_i))+1}\right)^{1/\nu}\pi_{\eta}^{(k)}(\varepsilon_i)\Big]^{1-\delta_i} \times \notag \\ &\Biggl[\left(\left(\frac{1}{\nu (\sum_{j=1}^{t-1}\exp(\rho(j)+\phi^TZ_i))+1}\right)^{1/\nu}-\left(\frac{1}{\nu (\sum_{j=1}^{t}\exp(\rho(j)+\phi^TZ_i))+1}\right)^{1/\nu}\pi_{\eta}^{(1)}(\varepsilon_i)\right)^{I_{(\varepsilon_i_i=1)}} \times \notag \\ &\left(\left(\frac{1}{\nu (\sum_{j=1}^{t-1}\exp(\rho(j)+\phi^TZ_i))+1}\right)^{1/\nu}-\left(\frac{1}{\nu (\sum_{j=1}^{t}\exp(\rho(j)+\phi^TZ_i))+1}\right)^{1/\nu}\pi_{\eta}^{(2)}(\varepsilon_i)\right)^{I_{(\varepsilon_i_i=2)}}\Biggr]^{\delta_i}.(1-p_i)\Biggr\}^{W_i(1-\xi_i)}. \end{align}
}

\end{document}

• I am using "align", but I check "split " too, and it was working. – Sedi Jan 26 '18 at 16:17
• The code as it stands will throw dozens of errors. Anyway, if you use equation and split all the \notags will suppress numbering. – campa Jan 26 '18 at 16:20
• the \notag s are in middle lines to avoid having multiple equation numbers. – Sedi Jan 26 '18 at 16:21
• Even when I write my equation in align environment only, the equation doesn't appear at all. If I remove the \scriptstyle it will appear but doesn't fit in my page. I though the combination of equation+align may help. – Sedi Jan 26 '18 at 16:30
• you can not have a align inside equation that surely gives an error? – David Carlisle Jan 26 '18 at 17:12

Unfortunately, a building block such as split or aligned (align is not permitted) inside equation does not allow for a page break. Instead use align as the only environment, and insert \notag to suppress unwanted numbering. Instead of reducing the size of the equation, introduce notation for large repeated expressions:

\documentclass{article}

\usepackage{amsmath}

\begin{document}

\mbox{}

\vspace{15cm}

{\allowdisplaybreaks
\begin{align} \label{Model}
\prod_{i=1}^{n}
&\biggl\{
\biggl[
\sum_{k=1}^{2}
x(\beta,i,t-1)-x(\beta,i,t)\pi_{\eta}^{(k)}(\varepsilon_i)
\biggr]^{1-\delta_i}
\notag \\
\Bigl[
\bigl(
x(\beta,i,t-1) - x(\beta,i,t)\pi_{\eta}^{(1)}(\varepsilon_i)
\bigr)^{I_{(\varepsilon_i=1)}}
\notag \\
&\hspace{4em} \times
\bigl(
x(\beta,i,t-1) -x(\beta,i,t)\pi_{\eta}^{(2)}(\varepsilon_i)
\bigr)^{I_{(\varepsilon_i=2)}}
\Bigr]^{\delta_i} \cdot p_i
\biggr\}^{W_i\xi_i} \notag \\
&\times
\biggl\{
\Bigl[
\sum_{k=1}^{2}
x(\phi,i,t-1) - x(\phi,i,t)\pi_{\eta}^{(k)}(\varepsilon_i)
\Bigr]^{1-\delta_i} \notag \\
\Bigl[
\bigl(
x(\phi,i,t-1)- x(\phi,i,t)\pi_{\eta}^{(1)}(\varepsilon_i)
\bigr)^{I_{(\varepsilon_i=1)}} \notag \\
&\hspace{4em} \times
\bigl(
x(\phi,i,t-1)-x(\phi,i,t)\pi_{\eta}^{(2)}(\varepsilon_i)
\bigr)^{I_{(\varepsilon_i=2)}}
\Bigr]^{\delta_i} \cdot (1-p_i)
\biggr\}^{W_i(1-\xi_i)},
\label{Model}
\end{align}
}
where $$x(A,i,t) = (\nu(\sum_{j=1}^{t} \exp(\rho(j)+A^{T}Z_{i}))+1)^{-1/\nu}$$
\end{document}