[Tex/LaTex] Overfull hbox in matrix

marginsmatrices

I am typing up a technical report that contains many large matrices. I am looking for a way to print these matrices with an equation number next to them without getting an overfull \hbox error.

I was thinking it might be possible to temporarily alter the page margins for the matrix. I don't really want to use smaller text as the matrix then starts becoming a little hard to read. This is currently what my matrix looks like. Any suggestions would really be appreciated. Thanks.

enter image description here

My code in creating the above matrix is as follows:

\documentclass[12pt]{article}

\usepackage[margin=1in]{geometry}
\usepackage{amsmath}
\setcounter{MaxMatrixCols}{20}    

\begin{document}

\begin{equation}
    \textbf{k}
    =
    \begin{bmatrix}
        \frac{EA}{L} & 0  & 0 & 0 & 0 & 0 & \frac{-EA}{L} & 0 & 0 & 0 & 0 & 0 \\
         & \frac{12EI_z}{L^3} & 0& 0& 0& \frac{6EI_z}{L^2} & 0& \frac{-12EI_z}{L^3} & 0 & 0& 0 &\frac{6EI_z}{L^2}  \\
         & & \frac{12EI_y}{L^3} & 0& \frac{-6EI_y}{L^2} & 0& 0& 0& \frac{-12EI_y}{L^3} & 0& \frac{-6EI_y}{L^2} & 0 \\
         & & & \frac{GI_p}{L} & 0 & 0 & 0 & 0 & 0 & \frac{-GI_p}{L} & 0 & 0 \\
         &  & & & \frac{4EI_y}{L}& 0 & 0& 0 & \frac{6EI_y}{L^2}& 0 & \frac{2EI_y}{L}  & 0 \\
         &  & & &  & \frac{4EI_z}{L} & 0 & \frac{-6EI_z}{L^2}& 0 & 0  & 0  & \frac{2EI_z}{L} \\
         &  &  &  & &  & \frac{EA}{L}  & 0 & 0  & 0 & 0 & 0  \\
         & & &  & & &  & \frac{12EI_z}{L^3}  & 0  & 0 & 0   & \frac{-6EI_z}{L^2} \\
         &   &  &  &  & & &  & \frac{12EI_y}{L^3}  & 0  & \frac{6EI_y}{L^2}  & 0 \\
         & &   & &  & & & &  & \frac{GI_p}{L}  & 0 & 0  \\
         & &  & & &  & & & & & \frac{4EI_y}{L}& 0  \\
         symm. & &  &   &  &  &  &  & &  && \frac{4EI_z}{L}                   
    \end{bmatrix}
    \label{kmat}
\end{equation}

\end{document}

Best Answer

I stopped symm extending the first column (don't use math italic for multi-letter words) and reduced the column padding a bit:

enter image description here

\documentclass[12pt]{article}

\usepackage[margin=1in]{geometry}
\usepackage{amsmath}
\setcounter{MaxMatrixCols}{20}


\begin{document}

\begin{equation}\setlength\arraycolsep{4pt}
    \textbf{k}
    =
    \begin{bmatrix}
        \frac{EA}{L} & 0  & 0 & 0 & 0 & 0 & \frac{-EA}{L} & 0 & 0 & 0 & 0 & 0 \\
         & \frac{12EI_z}{L^3} & 0& 0& 0& \frac{6EI_z}{L^2} & 0& \frac{-12EI_z}{L^3} & 0 & 0& 0 &\frac{6EI_z}{L^2}  \\
         & & \frac{12EI_y}{L^3} & 0& \frac{-6EI_y}{L^2} & 0& 0& 0& \frac{-12EI_y}{L^3} & 0& \frac{-6EI_y}{L^2} & 0 \\
         & & & \frac{GI_p}{L} & 0 & 0 & 0 & 0 & 0 & \frac{-GI_p}{L} & 0 & 0 \\
         &  & & & \frac{4EI_y}{L}& 0 & 0& 0 & \frac{6EI_y}{L^2}& 0 & \frac{2EI_y}{L}  & 0 \\
         &  & & &  & \frac{4EI_z}{L} & 0 & \frac{-6EI_z}{L^2}& 0 & 0  & 0  & \frac{2EI_z}{L} \\
         &  &  &  & &  & \frac{EA}{L}  & 0 & 0  & 0 & 0 & 0  \\
         & & &  & & &  & \frac{12EI_z}{L^3}  & 0  & 0 & 0   & \frac{-6EI_z}{L^2} \\
         &   &  &  &  & & &  & \frac{12EI_y}{L^3}  & 0  & \frac{6EI_y}{L^2}  & 0 \\
         & &   & &  & & & &  & \frac{GI_p}{L}  & 0 & 0  \\
         & &  & & &  & & & & & \frac{4EI_y}{L}& 0  \\
         \rlap{\textit{symm.}} & &  &   &  &  &  &  & &  && \frac{4EI_z}{L}                   
    \end{bmatrix}
    \label{kmat}
\end{equation}

\end{document}
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