# [NTG-context] Math alignment

Hans Aberg haberg-1 at telia.com
Tue Jul 7 21:11:58 CEST 2015

> On 7 Jul 2015, at 20:17, Wolfgang Schuster <schuster.wolfgang at gmail.com> wrote:

> You can set the alignment for each column in a matrix with the align key.

FYI, the document amshelp.pdf says that AMS-LaTeX environments align, align*, and aligned, can have multiple alignments, and gives this example:
\begin{align*}
K &\approx G * H&   i&= j+k&  B &\subset C\\
H &\approx A_{0}*B_{0}&  i’&= j’+k’&  C &= D\cap E\\
G &\approx \coprod_{\alpha\in A} L_{\alpha}&  i’’&=j’’+k’’& A &= D \cup E
\end{align*}
which is typeset so that 'K &\approx G * H’ is one equation aligned on the ‘&’ with the others below, followed by 'i&= j+k’ in the next column.

So the ampersands have multiple functions here, it seems: alignment and separating columns.

Translating into ConTeXt, one might have (pseudocode):
\startformula
\startalign
\NC K \NA \approx G * H \NC  i\NA= j+k \NC B \NA \subset C \NR
\NC H \NA \approx A_{0}*B_{0} \NC   i’\NA= j’+k’ \NC   C \NA = D\cap E\NR
\NC G \NA \approx \coprod_{\alpha\in A} L_{\alpha}
\NC   i’’\NA =j’’+k’’ \NC  A \NA = D \cup E \NR
\stopalign
\stopformula
where I have introduce a symbol \NA for alignment.