
\documentclass[conference,twocolumn]{IEEEtran}
\usepackage{amsmath,lipsum}
\begin{document}
\begin{figure*}[!t]
\normalsize
\begin{equation}
e^{At}=\left[
\begin{array}{ccc}
3e^{-t}-3e^{-2t}+e^{-3t} & \dfrac{5}{2}e^{-t}-4e^{-2t}+\dfrac{3}{2}e^{-3t} & \dfrac{1}{2}e^{-t}-e^{-2t}+\dfrac{1}{2}e^{-3t} \\[1em]
-3e^{-t}+6e^{-2t}-3e^{-3t} & \dfrac{-5}{2}e^{-t}+8e^{-2t}-\dfrac{9}{2}e^{-3t} & \dfrac{-1}{2}e^{-t}+2e^{-2t}-\dfrac{3}{2}e^{-3t} \\[1em]
3e^{-t}-12e^{-2t}+9e^{-3t} & \dfrac{5}{2}e^{-t}-16e^{-2t}+\dfrac{27}{2}e^{-3t} & \dfrac{1}{2}e^{-t}-4e^{-2t}+\dfrac{9}{2}e^{-3t}
\end{array}\right]
\end{equation}
\hrulefill
\vspace*{4pt}
\end{figure*}
\lipsum[1-10]
\begin{align}
&e^{At}=\notag\\
&\begin{bmatrix}
3 \alpha-3 \beta+\gamma & \dfrac{5}{2} \alpha-4 \beta+\dfrac{3}{2} \gamma & \dfrac{1}{2} \alpha-\beta+\dfrac{1}{2} \gamma \\[1em]
-3 \alpha+6 \beta-3 \gamma & \dfrac{-5}{2} \alpha+8 \beta-\dfrac{9}{2} \gamma & \dfrac{-1}{2} \alpha+2 \beta-\dfrac{3}{2} \gamma \\[1em]
3 \alpha-12 \beta+9 \gamma & \dfrac{5}{2} \alpha-16 \beta+\dfrac{27}{2} \gamma & \dfrac{1}{2} \alpha-4 \beta+\dfrac{9}{2} \gamma
\end{bmatrix}
\end{align}
where $\alpha=e^{-t}$, $\beta=e^{-2t}$, and $\gamma=e^{-3t}$.
\lipsum[11-15]
\end{document}
You can always substitute the large symbols or partial expressions with shorter ones. In this case, assuming \alpha
, \beta
, and \gamma
are not used before, you can replace e^{-t}
, e^{-2t}
, and e^{-3t}
by the shorter \alpha
, \beta
, and \gamma
, respectively.
The second approach is to place the equation at the top of the next page followed by an \hrulefill
. In this case, the equation will span the two columns. Also, you should introduce the equation some how earlier to let it appear in the right place. The equation is wrapped into a figure*
environment with choosing the [!t]
specifier for LaTeX to try very hard to place the equation at the top of the next page.
See Page 8 of How to Use the IEEEtran LATEX Class for more details.
*
to denote multiplication?\begin{bmatrix}\end{bmatrix}
. Also, use\\[1em]
to change line instead of insert blank lines.