How to Adjust the Font Size of an Equation?

Question

I have an equation in a double column context. As can be seen from the picture below, the equation is just a little bit wider than a single column. I do not want to create a span-column equation for it. Is there a way I can change it to a smaller font size so it will fit in one column?

I am editing the file in LyX, so it would be great if there is a way to do it directly in Lyx. If not, LaTeX codes are also acceptable.

After changing to \bmatrix as suggested by @daleif, it look like

Can the space between the two matrices on the left hand side and the spaces between columns of the first matrix be further reduced?

Answer 1

You can either reduce the value \arraycolsep and use the fleqn environment from nccmath, or use the medsize environment, also from nccmath, which reduces the font size to about 80 % of \displaystyle.

\documentclass{ieeetran}
\usepackage{amsmath, nccmath}
\usepackage{lipsum}

 \begin{document}

\lipsum[1]

\begin{fleqn}
  \begin{equation}
    \setlength{\arraycolsep}{3pt}
    \begin{bmatrix}
      -k_w + \sin α₁ & -k_w +1 & -k_w + \sin α₁ \\
      \sin 5α₁ & 1 & \sin 5α₁ \\
      \sin 7α₁ & -11 & \sin7α₁ \\
    \end{bmatrix}
    \!
    \begin{bmatrix}
      N₁ \\ N₂ \\ N₃
    \end{bmatrix}
    =
    \begin{bmatrix}
      0 \\ 0 \\ 0
    \end{bmatrix}
  \end{equation}
\end{fleqn}

\lipsum[3]

\begin{equation}
  \begin{medsize}
    \begin{bmatrix}
      -k_w + \sin α₁ & -k_w +1 & -k_w + \sin α₁ \\
      \sin 5α₁ & 1 & \sin 5α₁ \\
      \sin 7α₁ & -11 & \sin7α₁ \\
    \end{bmatrix}
    \!
    \begin{bmatrix}
      N₁ \\ N₂ \\ N₃
    \end{bmatrix}
    =
    \begin{bmatrix}
      0 \\ 0 \\ 0
    \end{bmatrix}
  \end{medsize}
\end{equation}
\lipsum[3]

\end{document} 

Answer 2

I can reproduce the second picture in the question with

\documentclass[11pt]{IEEEtran}
\usepackage{amsmath}
\usepackage{newtxtext,newtxmath}

\usepackage{lipsum}

\begin{document}

\setcounter{equation}{30} % to reproduce the example

\lipsum*[2]
\begin{equation}
\begin{bmatrix}
  -k_w + \sin \alpha_1 & -k_w +1 & -k_w + \sin \alpha_1 \\
  \sin 5\alpha_1 & 1 & \sin 5\alpha_1 \\
  \sin 7\alpha_1 & -11 & \sin7\alpha_1 \\
\end{bmatrix}
\begin{bmatrix}
  N_1 \\ N_2 \\ N_3
\end{bmatrix}
=
\begin{bmatrix}
0 \\ 0 \\ 0
\end{bmatrix}
\end{equation}
\lipsum

\end{document} 

I find it unacceptable that a big organization like IEEE still uses

\renewcommand{\rmdefault}{ptm}

and Computer Modern for math.

An immediate improvement can be obtained by doing \usepackage{mathptmx} together with a trick for pushing the equation far left and decreasing locally \arraycolsep:

\documentclass[11pt]{IEEEtran}
\usepackage{amsmath}
\usepackage{mathptmx}

\usepackage{lipsum}

\begin{document}

\setcounter{equation}{30} % to reproduce the example

\lipsum*[2]
\begin{equation}
\addtolength{\arraycolsep}{-3pt}
\hfilneg
\begin{bmatrix}
  -k_w + \sin \alpha_1 & -k_w +1 & -k_w + \sin \alpha_1 \\
  \sin 5\alpha_1 & 1 & \sin 5\alpha_1 \\
  \sin 7\alpha_1 & -11 & \sin7\alpha_1 \\
\end{bmatrix}
\begin{bmatrix}
  N_1 \\ N_2 \\ N_3
\end{bmatrix}
=
\begin{bmatrix}
0 \\ 0 \\ 0
\end{bmatrix}
\hspace{1000 pt minus 1fil}
\end{equation}
\lipsum

\end{document} 

Better yet with

\usepackage{newtxtext,newtxmath}

instead of \usepackage{mathptmx}: