General ⇒ Matrix Alignment

[wintermute01]

Hello all,

I need help in aligning some long math in a matrix. I have tried the array format and it still doesn't work. My margins are 1.25in all around and simply inputting them as is results in the equation going outside the page. Breaking the math up into sections makes it get treated as different elements and therefore go out of alignment.
Here's the tex code with the array setting ( I used "bmatrix" with similar results):

Code: Select all

\begin{equation}
e^{[\mathbf{M}]}=
\left[\begin{array}{c c}
\cosh((\sqrt{k^2 - \hat{\sigma}^2})z)+\frac{i\hat{\sigma}}{(\sqrt{k^2-\hat{\sigma}^2})} \sinh((\sqrt{k^2-\hat{\sigma}^2})z) & \frac{i k}{(\sqrt{k^2 - \hat{\sigma}^2})} \sinh((\sqrt{k^2 -\hat{\sigma}^2})z)\\
\frac{-i k}{(\sqrt{k^2 - \hat{\sigma}^2})} \sinh((\sqrt{k^2 -\hat{\sigma}^2})z) & \cosh((\sqrt{k^2 - \hat{\sigma}^2})z) + \frac{-i \hat{\sigma}}{(\sqrt{k^2 - \hat{\sigma}^2})} \sinh((\sqrt{k^2 -\hat{\sigma}^2})z)
\end{array}\right]
\end{equation}

Thanks!

[Juanjo]

My first tentative has been

Code: Select all

\begin{equation}
   e^{[\mathbf{M}]}=
   \begin{bmatrix}
      \cosh(z\sqrt{k^2 - \hat{\sigma}^2}) 
         +\frac{i\hat{\sigma}}{\sqrt{k^2-\hat{\sigma}^2}} \sinh(z\sqrt{k^2-\hat{\sigma}^2}) 
      & \frac{i k}{\sqrt{k^2 - \hat{\sigma}^2}} \sinh(z\sqrt{k^2 -\hat{\sigma}^2})  \\[3ex]
      \frac{-i k}{\sqrt{k^2 - \hat{\sigma}^2}} \sinh(z\sqrt{k^2 -\hat{\sigma}^2}) 
      & \cosh(z\sqrt{k^2 - \hat{\sigma}^2}) 
         + \frac{-i \hat{\sigma}}{\sqrt{k^2 - \hat{\sigma}^2}} \sinh(z\sqrt{k^2 -\hat{\sigma}^2})
   \end{bmatrix}
\end{equation}

But I wonder if it is absolutely neccesary to keep the square root in the above expression. So why not introduce a new notation, say $\mu=\sqrt{k^2 - \hat{\sigma}^2}$ ? In this way, the matrix fits easily in a page:

Code: Select all

\begin{equation}
   e^{[\mathbf{M}]}=
   \begin{bmatrix}
      \cosh(\mu z) +\frac{i\hat{\sigma}}{\mu} \sinh(\mu z) 
      & \frac{i k}{\mu} \sinh(\mu z)  \\[3ex]
      \frac{-i k}{\mu} \sinh(\mu z) 
      & \cosh(\mu z) + \frac{-i \hat{\sigma}}{\mu} \sinh(\mu z)
   \end{bmatrix}
\end{equation}

Of course, I assume you are using the amsmath package.

[balf]

I propose this code:
\setlength{\arraycolsep}{-6pt}\renewcommand{\arraystretch}{1.5}
\begin{multline}
e^{[\mathbf{M}]}=\\
\begin{medsize}
\left[\begin{matrix} \cosh(\sqrt{k^2 -
\hat{\sigma}^2}z)+\dfrac{i\hat{\sigma}}{\sqrt{k^2-\hat{\sigma}^2}}
\sinh(\sqrt{k^2-\hat{\sigma}^2}z)
& \dfrac{i k}{\sqrt{k^2 - \hat{\sigma}^2}} \sinh(\sqrt{k^2 -\hat{\sigma}^2}z)\\
\dfrac{-i k}{\sqrt{k^2 - \hat{\sigma}^2}} \sinh(\sqrt{k^2 -\hat{\sigma}^2}z) & \cosh(\sqrt{k^2 -
\hat{\sigma}^2}z) + \dfrac{-i \hat{\sigma}}{\sqrt{k^2 - \hat{\sigma}^2}} \sinh(\sqrt{k^2
-\hat{\sigma}^2}z)
\end{matrix}\right]
\end{medsize}
\end{multline}

As you can see I suppressed some unnecessary (in my opinion) parentheses. You also can slightly change the margin. You need to load the nncmath packaage (from the ncctools bundle), which defines a series of useful medium-size commands.

Best regards,
B.A.

[localghost]

The problem could be solved by changing the character size in the coulmns of the array with help of the array package.

Code: Select all

\documentclass[BCOR13mm,DIV15]{scrartcl}
\usepackage{amsmath}
\usepackage{array}

\begin{document}
  \begin{equation}
    e^{[\boldsymbol{M}]}=
    \left[
    \begin{array}{>{\scriptstyle}c>{\scriptstyle}c}
      \cosh((\sqrt{k^2 - \hat{\sigma}^2})z)+\frac{i\hat{\sigma}}{(\sqrt{k^2-\hat{\sigma}^2})} \sinh((\sqrt{k^2-\hat{\sigma}^2})z) & \frac{i k}{(\sqrt{k^2 - \hat{\sigma}^2})} \sinh((\sqrt{k^2 -\hat{\sigma}^2})z) \\
      \frac{-i k}{(\sqrt{k^2 - \hat{\sigma}^2})} \sinh((\sqrt{k^2 -\hat{\sigma}^2})z) & \cosh((\sqrt{k^2 - \hat{\sigma}^2})z) + \frac{-i \hat{\sigma}}{(\sqrt{k^2 - \hat{\sigma}^2})} \sinh((\sqrt{k^2 -\hat{\sigma}^2})z)
    \end{array}
    \right]
  \end{equation}
\end{document}

Best regards
Thorsten¹