[NTG-context] Math equation with indentation

[Aditya Mahajan]

On Tue, 13 May 2008, 302302 wrote:

> Hi,
> I need to use a multieqaution in this form ( http://img233.imageshack.us/img233/2372/eqsx3.png ). I am mostly interested in the right brace and the indentation after the "subject to". I tried to use mathmatrix but without success. Can you help me with it?

I am using nested matrices, but this is one case which will be best solved 
by something equivalent for gathered and aligned. It has been on my todo 
list for a long time.

Here is a solution using nested matrices, where I use \noalign to fake 
correct spacing after the first line (and changed the \cdots in the last 
condition to \dots).

\definemathmatrix[rightbrace][left={\left.},right={\,\right\}},n=1,align=left]

\starttext

\placeformula[+] \startformula
\startrightbrace
   \NC \min \{c_1 x_1 + c_2 x_2 + \cdots + c_n x_n \} \NR
       \noalign{\vskip 0.2em}
   \NC \text{subject to} \NR
   \NC \quad
       \startmathmatrix[n=9,align={middle,middle,middle,
         middle,middle,middle,right,middle,middle},
         distance=0.3em]
         \NC a_{11} x_1 \NC + \NC a_{12} x_2 \NC +
         \NC \cdots \NC + \NC a_{1n} x_n \NC = \NC b_1 \NR
         \NC a_{21} x_1 \NC + \NC a_{22} x_2 \NC +
         \NC \cdots \NC + \NC a_{2n} x_n \NC = \NC b_2 \NR
         \NC            \NC   \NC  \vdots    \NC
         \NC        \NC   \NC            \NC   \NC \vdots \NR
         \NC a_{m1} x_1 \NC + \NC a_{m2} x_2 \NC +
         \NC \cdots \NC + \NC a_{mn} x_n \NC = \NC b_m \NR
         \NC            \NC   \NC            \NC
         \NC        \NC
         \NC \llap{x_1,x_2,\dots,x_n} \NC \ge \NC 0.
       \stopmathmatrix \NR
   \stoprightbrace
\stopformula

\stoptext


Aditya