Math & Science ⇒ Math Mode Issue

[sergio_6280]

I have the same problem as described here (more or less). I need to write two matrix in a row like (something)=(something else) but I would like also the number of the equation to refer to it with \vref.
I'm using this:

Code: Select all

\begin{equation}
\left( {\begin{array}{*{20}{c}}
A&B\\
C&D
\end{array}} \right) $=$ \left( {\begin{array}{*{20}{c}}
0&{jK}\\
{\frac{1}{jK}}&0
\end{array}} \right)
\end{equation}

but there are these problems:

Code: Select all

Missing $ inserted
Display math should end with $$
Missing $ inserted \left
Missing $ inserted
Bad math environment delimiter. \end{equation}
You can't use `\eqno' in vertical mode \end{equation}
Missing $ inserted \end{equation}
Display math should end with $$ \end{equation}

What is wrong?
Thanks

[localghost]

You should always provide a self-contained and minimal example to give an adequate problem description.

I have some questions.

• Why do you write $=$ inside a math environment? This causes your problem here.
• Why do you enclose the {array} in additional curly braces?
• Why do you use an {array} with 20 columns if you need only two?

The amsmath package (in the below code loaded by mathtools) makes math typesetting easier.

Code: Select all

\documentclass[11pt]{article}
\usepackage[T1]{fontenc}
\usepackage{mathtools}  % loads »amsmath«

\begin{document}
  \begin{equation}
    \begin{pmatrix}
      A & B \\
      C & D
    \end{pmatrix}
    =
    \begin{pmatrix}
      0 & jK \\
      \frac{1}{jK} & 0
    \end{pmatrix}
    \end{equation}
\end{document}

For details consult the respective manuals. On the command line you can get instantly.

Code: Select all

texdoc amsmath

Further reading:

• The »Math mode« document.

Best regards and welcome to the board
Thorsten

[sergio_6280]

Sorry for all my mistakes. It was the first time I was asking in this kind of forum. I will try to be more clear next time. Anyway, your code works. So thank you. Thank you also for the link of the "Math mode" guide.