[Tex/LaTex] How to format multiple equations properly

equations

When I specify a set of partial differential equations, I usually have to write out not only the equation itself, but also its domain. To complete the problem, I need to specify the boundary conditions underneath it in the same fashion. So the information I need to write is of the format:

EQUATIONS in DOMAIN
CONDITIONS in BOUNDARY

Using simple \[ ... \] format, it looks absolutely horrible. So I tried using a 2×2 array using \begin{array}{cc}...\end{array}, but this doesn't look correct either. What is the standard approach to formatting these equations?

Update: This is what I have coded thus far:

 \[ \begin{array}{cc} -\nabla^2u=0, & \Omega\\u=g & \partial\Omega \end{array}\]

Best Answer

You can probably use the align environment:

enter image description here

\documentclass{article}
\usepackage{amsmath}
\begin{document}
     \begin{align*}
     -\nabla^2u&=0,\quad \Omega\\
     u&=g \quad \partial\Omega
     \end{align*} 

% alignat option added

     \begin{alignat*}{2}
       -\nabla^2u&=0,&\quad &\Omega\\
                u&=g &      &\partial\Omega
     \end{alignat*} 
\end{document}

For further reading about alignment, check amsldoc under Displayed equations. About \quad, it is defined as:

\def\quad{\hskip 1em\relax}
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