General ⇒ Aligning a system of linear equations

[Plato]

Code: Select all

\documentclass[11pt,a4paper,openany]{report}
\usepackage{amssymb,amsmath,amsthm}
\usepackage[dutch]{babel}
\usepackage{mdframed}
\usepackage{systeme,mathtools}
\usepackage{lipsum}
\usepackage{relsize}
\newcommand\md{\ }
\renewcommand{\qedsymbol}{$\blacksquare$}
\begin{document}

\systeme{x_1=2r + s -t,x_2= r, x_3=-2s +2t, x_4=s, x_5=t}

Hello, I want to align a system of equations such that the x_1, x_2, x_3, x_4, x_5 are all underneath each other. Right now I get my system in staircase-form, like:
x_1 = 2r + s - 3t
......x_2 = r
...........x_3 = -2s + 2t
(there is empty space where the dots are) etc. I want all the x_i's aligned nicely under each other. Can someone help me with this? Thank you in advance.

[Johannes_B]

That is the expected behaviour of the package, try the cases-environment instead.

Code: Select all

\documentclass[11pt,a4paper,openany]{report}
\usepackage{amssymb,amsmath,amsthm}
\usepackage[dutch]{babel}
\usepackage{mdframed}
\usepackage{systeme,mathtools}
\usepackage{lipsum}
\usepackage{relsize}
\newcommand\md{\ }
\renewcommand{\qedsymbol}{$\blacksquare$}
\begin{document}

\systeme{x_1=2r + s -t,x_2= r, x_3=-2s +2t, x_4=s, x_5=t}
\[\begin{cases}x_1=2r + s -t\\x_2= r\\ x_3=-2s +2t\\ x_4=s\\ x_5=t
	\end{cases}
\]
\end{document}

[Stefan Kottwitz]

To add to what Johannes, said, that package is for aligning terms and signs vertically, such that there's a column for each variable. That's especially good if you got several variables in each row. However, it may look a bit strange in the case of a single variable in each row when all are different. That's the case above.

As Johannes wrote, cases fits better here and is easy to write. In the current situation the terms at the left have roughly the same width. But if you got different widths, it could be good to use additional alignment. Here I change x_5 to x_{10} just as a demonstration. I used the aligned environment instead.

Code: Select all

\documentclass[11pt,a4paper,openany]{report}
\usepackage{amssymb,amsmath,amsthm}
\usepackage[dutch]{babel}
\usepackage{mdframed}
\usepackage{systeme,mathtools}
\usepackage{lipsum}
\usepackage{relsize}
\newcommand\md{\ }
\renewcommand{\qedsymbol}{$\blacksquare$}
\begin{document}
\systeme{x_1=2r + s -t,x_2= r, x_3=-2s +2t, x_4=s, x_10=t}
\[\begin{cases}x_1=2r + s -t\\x_2= r\\ x_3=-2s +2t\\ x_4=s\\ x_{10}=t
        \end{cases}
\]
\[
  \left\{\begin{aligned}
    x_1    &= 2r + s -t \\
    x_2    &= r         \\
    x_3    &= -2s + 2t  \\
    x_4    &= s         \\
    x_{10} &= t
  \end{aligned}\right.
\]
\end{document}

Stefan