General ⇒ parenthesis problems

[Martin]

Hi, I am Martin Gimenez. I have the following problem:
I want to write a very long equation, so i use eqnarray and I separate the equation in several rows and columns. The problem is that I want to write two rows between a big parenthesis, but it seems that this is not allowed...

I hope you can help me, thank you very much!!!

[gmedina]

Hi Martin,

In the first place you shouldn't use eqnarray anymore. Reasons can be found in l2tabu (available in several languages) and in Avoid eqnarray! In its stead you should use align or any other of the environments provided by the amsmath package. In second place, without a better description of your equation and the desired layout, it's really difficult to give you the best solution. Perhaps the amsmath documentation or the Mathmode document can give you some ideas on how to present your equation. If your problems persist, then please try to give us a concrete example of what you desire to achieve.

[Juanjo]

As pointed out by gmedina, never use the obsolete eqnarray environment and replace them by the amsmath environments. As a small example of a few of them (with braces joining two rows), try this:

Code: Select all

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{equation*}
   \left.
   \begin{gathered}
      f(x,y)=2x-y+xy \\
      \nabla f(x,y)=\mathbf{0}
   \end{gathered}
   \right\}\Longrightarrow\left.
   \begin{alignedat}{2}
      f_x(x,y)&={} & 2 &+y=0 \\
      f_y(x,y)&={} & -1 &+x=0
   \end{alignedat}
   \right\}\Longrightarrow (x,y)=(1,-2)
\end{equation*}
\end{document}

[Martin]

Ok! thank you very much for your help, I appreciate it!