Dots in a system of constraints

Question

I would like to write a linear program as follows:

enter image description here

The text above and below is shown only to indicate the position of the system on the page.

I wrote

\documentclass[a4paper,11pt]{report}
\usepackage[italian]{babel}
\usepackage{amsmath}

\begin{document}

\begin{align}
& \text{max (o min)} & c_1 x_1 &+ \dots + c_n x_n \\
& \text{soggetto a} & a_{11} x_1 &+ \dots + a_{1n} x_n \sim b_1 \\
&& a_{m1} x_1 &+ \dots + a_{mn} x_n \sim b_m,
\end{align}

\end{document}

but I hadn't the same result. In particular to the space between words and system, and I do not know how to insert the dots vertical.

score 4 · Accepted Answer · edited Jun 10 '20 at 12:32

4

Use \vdots for the vertical dots, and I'd recommend using an alignat to achieve the desired result:

enter image description here

You can also get the variables right aligned with a bit more work:

enter image description here

Notes:

I also replaced the \dots with \dotsb. See Difference of the \dots* for more details.

Code:

\documentclass{report}
\usepackage{amsmath}
\begin{document}
\begin{alignat}{5}
& \text{max (o min) } &c_1 x_1     &{}+ \dotsb &&{}+ c_n x_n \
& \text{soggetto a }  &a_{11} x_1  &{}+ \dotsb &&{}+ a_{1n} x_n &&{}\sim b_1 \\nonumber
&                                  &    \vdots \
&                     & a_{m1} x_1 &{}+ \dots &&{}+ a_{mn} x_n &&{}\sim b_m
\end{alignat}
If you want the variables right aligned:
\begin{alignat}{6}
& \text{max (o min) } &c_1 x_1     &&{}+ \dotsb &&{}+{} &&c_n x_n \
& \text{soggetto a }  &a_{11} x_1  &&{}+ \dotsb &&{}+{} &&a_{1n} x_n &{}\sim b_1 \\nonumber
&                                  &&    \vdots \
&                     & a_{m1} x_1 &&{}+ \dotsb &&{}+{} &&a_{mn} x_n &{}\sim b_m
\end{alignat}
\end{document}

edited Jun 10 '20 at 12:32

Community

1

answered May 20 '14 at 22:30

Peter Grill

223,288

\dotsb behaves like a binary operator: if nothing follows it, no space is added. Thus, the + \dotsb & in the second example should be + \dotsb {}& – Dan May 20 '14 at 23:53
And to obtain also "tilda" (~) aligned? – Pippothedog May 21 '14 at 12:42
there is more space before the second plus than after the first one. this can be fixed by removing the {} before the second plus, since \dotsb already takes care of it. – barbara beeton May 21 '14 at 13:22
@Pippothedog: Have updated solution to align the ~ as well. – Peter Grill May 22 '14 at 06:04

Dots in a system of constraints

1 Answers1

Notes:

Code: