[Tex/LaTex] How to break equations in between multiple cases environment

amsmathcases

I was wondering if anyone could assist me with the the following problem: The equation below has 4 different blocks and is too long to fit on one line. Ideally I would like to break it into two and put one half below the first half. Any ideas how to do this? I've tried \\ and aligned but don't seem to be getting the right results. 

\documentclass{article}
\usepackage{amsmath}

\begin{document}


\begin{equation}  \label{int_num_test}  
x_{i}  = \eta1 \times \begin{cases} 
(1 + \eta8(age - 5.4)) & age \le 10\\
(1 + \eta9(age - 5.4)) & age > 10\\ 
\end{cases}
\times
\begin{cases}
1 & \text{Case 1}\\
1 + \eta12 & \text{Case 2}\\
1 + \eta13  & \text{Case 3}\\
1 + \eta14 & \text{Case 4}\\
\end{cases}   \times 
\begin{cases}
1 & Case 5\\
1 + \eta10 & Case 6\\
\end{cases} \times 
(1 + \eta11(v - 5.08))
\end{equation}


\end{document}

Best Answer

Hmm a couple of alternatives here, neither particularly readable, I'd be tempted to define variables for the case terms and then just show it as a\times b\times c \times d but

enter image description here

\documentclass{article}
\usepackage{amsmath}

\begin{document}
\newcommand\age{\mathrm{age}}

\begin{equation}  \label{int_num_test}  
\begin{split}
x_{i}  = \eta1 \times \begin{cases} 
(1 + \eta8(\age - 5.4)) & \age \le 10\\
(1 + \eta9(\age - 5.4)) & \age > 10\\ 
\end{cases}
\times
\begin{cases}
1 & \text{Case 1}\\
1 + \eta12 & \text{Case 2}\\
1 + \eta13  & \text{Case 3}\\
1 + \eta14 & \text{Case 4}\\
\end{cases} \\
  \times 
\begin{cases}
1 & \text{Case 5}\\
1 + \eta10 & \text{Case 6}\\
\end{cases} \times 
(1 + \eta11(v - 5.08))
\end{split}
\end{equation}
or
\begin{equation}  \label{int_num_testq}  
\begin{gathered}
x_{i}  = \eta1 \times \begin{cases} 
(1 + \eta8(\age - 5.4)) & \age \le 10\\
(1 + \eta9(\age - 5.4)) & \age > 10\\ 
\end{cases}\\
\times
\begin{cases}
1 & \text{Case 1}\\
1 + \eta12 & \text{Case 2}\\
1 + \eta13  & \text{Case 3}\\
1 + \eta14 & \text{Case 4}\\
\end{cases} \\
\qquad  \times 
\begin{cases}
1 & \text{Case 5}\\
1 + \eta10 & \text{Case 6}\\
\end{cases}\\
\qquad\qquad \times 
(1 + \eta11(v - 5.08))
\end{gathered}
\end{equation}

\end{document}
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