Aligning across 'aligned' equation blocks

I'd like to format two groups of equations such that all their equal signs line up and such that I can put a big brace to the right of each block to annotate that block. The last part is easily achieved using the aligned environment of amsmath:

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{align}
\left.\begin{aligned}
\alpha_X \times \alpha_Y &= \chi \\
\alpha_X \times \beta_Y &= \xi \\
\beta_X \times \beta_Y &= \zeta
\end{document}


Equal signs as well as the big braces line up:

• This is not exactly what I hoped for (since it still involves whitespace fiddling), but in the absence of better alternatives, I think this is a good solution. So, thanks! – Torsten Schönfeld Aug 24 '10 at 9:29

I have a solution as well. It is taken from the MathMode documentation on CTAN, page 112.

\documentclass{article}
\usepackage{amssymb}
\usepackage{amsmath}
\newcommand{\fakealign}{%
\mbox{\hspace{5cm}} & \mbox{\hspace{5cm}} \nonumber\\%
}
\begin{document}
An equation;
\vspace{-1cm}
\begin{align}
\fakealign
D &= I\left(1+r\right)^t
\end{align}
Equation with a long left hand side;
\vspace{-1cm}
\begin{align}
\fakealign
\left(1+d\right)^{-T} &= U
\end{align}
Equation with a long right hand side
\vspace{-1cm}
\begin{align}
\fakealign
PV &= \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}
\end{align}
They all align with the = sign :)
\end{document}


I can't post an image because I am a new user and therefore don't have enough reputation. But build it and observe!

I think this simpler and more elegant than Stefan's solution, but hey. Horses for courses.

Enjoy!

• Nice solution! I think it would be even more elegant if you would add the negative vertical space at the end of the line in the macro: \[-1cm] – lex82 Mar 3 '13 at 16:53