Math & Science ⇒ Matrix within a matrix

[davefulton]

Hello all,
I am trying to get this array

Code: Select all

\begin{equation}U = \left( \begin{array}{c}
\rho\\
\rho u\\
\rho v\end{array} \right),\end{equation}

into the values marked x in this array

Code: Select all

\[ F^+(U) = \left\{ \begin{array}{ll}
         x & \mbox{$x \geq 0$};\\
         x & \mbox{$x \geq 0$};\\
        -x & \mbox{$x < 0$}.\end{array} \right. \]

so something like

Code: Select all

\[ F^+(U) = \left\{ \begin{array}{ll}
     \begin{equation}U = \left( \begin{array}{c}
     \rho\\
     \rho u\\
     \rho v\end{array} \right),\end{equation}        
     & \mbox{$x \geq 0$};\\
         x & \mbox{$x \geq 0$};\\
        -x & \mbox{$x < 0$}.\end{array} \right. \]

however this won't compile. Any help

[Stefan Kottwitz]

Hi,

it would work without the equation environment:

Code: Select all

\[ F^+(U) = \left\{ \begin{array}{ll}
     U = \left( \begin{array}{c}
     \rho\\
     \rho u\\
     \rho v\end{array} \right),
     & \mbox{$x \geq 0$};\\
         x & \mbox{$x \geq 0$};\\
        -x & \mbox{$x < 0$}.\end{array} \right. \]

Stefan

[php1ic]

As another option, try using the 'cases' environment together with the 'pmatrix' environment provided by the amsmath package.

Code: Select all

\documentclass{article}

\usepackage{amsmath}

\begin{document}

\[
F^+(U) =
  \begin{cases}
\begin{pmatrix}
\rho\\
\rho u\\
\rho v
\end{pmatrix} & \mbox{$x \geq 0$};\\[5ex]
\begin{pmatrix}
\rho\\
\rho u\\
\rho v
\end{pmatrix} & \mbox{$x \geq 0$};\\[5ex]
-\begin{pmatrix}
\rho\\
\rho u\\
\rho v
\end{pmatrix} & \mbox{$x < 0$}
  \end{cases}
\]

\end{document}

[davefulton]

Thank you, thank you, thank you x

[localghost]

Now that the problem is solved, please mark the topic accordingly as described in Section 3 of the Board Rules. This applies to all your other requests.


Best regards
Thorsten