[texhax] Aligning multiline formulae

Barbara Beeton bnb at ams.org
Tue Dec 9 15:29:41 CET 2003

ian watson is trying to get a multiline formula to
left-align.  he is using the package amsmath.
the example he sent does not indicate any alignment
points (although in the gathered environment they
would be inappropriate).

would this be close enough?

\begin{align*}
\mathbf{A}&\equiv\begin{bmatrix}a_{11} & a_{12} \\ a_{21} & a_{22}\end{bmatrix}%
\equiv\begin{bmatrix}1 & -1 \\-c & 1\end{bmatrix}, \\
\mathbf{x}&\equiv\begin{bmatrix}x_1 \\ x_2\end{bmatrix}%
\equiv\begin{bmatrix}Y \\X\end{bmatrix}, \\
\mathbf{b}&\equiv\begin{bmatrix}b_1  \\ b_2\end{bmatrix}%
\equiv\begin{bmatrix}I^* \\a\end{bmatrix}.
\end{align*}

note the & before the first \equiv on each line; that
sets the alignment point, and since there is only a
single letter on the left of each line, aligning the
relations makes the left edge very close to even.

i suggest taking a closer look at the brief amsmath
manual, available as a pdf file from the ams web site:
http://www.ams.org/tex/amslatex.html
-- bb