# Problem related with aligned

I'm trying to place 3 equations with some dots between them and I don't know why only the first \cdots is right aligned and the others are a mess. This is the code:

\begin{aligned} (\mathcal{H}_{11}- &S_{11}E_i)c_{1i}+(\mathcal{H}_{12}- &S_{12}E_i)c_{2i}+ &\cdots+(\mathcal{H}_{1n}- &S_{1n}E_i)c_{ni}=0\\ (\mathcal{H}_{21}- &S_{21}E_i)c_{1i}+(\mathcal{H}_{22}- &S_{22}E_i)c_{2i}+ &\cdots+(\mathcal{H}_{2n}- &S_{2n}E_i)c_{ni}=0\\ &\cdots&\cdots&\cdots&\cdots\\ (\mathcal{H}_{n1}- &S_{n1}E_i)c_{ni}+(\mathcal{H}_{n2}- &S_{n2}E_i)c_{2i}+ &\cdots+(\mathcal{H}_{nn}- &S_{nn}E_i)c_{ni}=0\\ \label{eq:secular} \end{aligned}


Thank you very much

Edit: Thanks everyone for the help, maybe an image about what i'm trying to obtain would be better than words:

• You have to think on it like this: You need a & for each alignment point, and a & between each set of alignments (left and right pairs around an alignment &), so you need to figure out which &'s does what. It is not clear to me which parts should be aligned in your example. – daleif Apr 8 '16 at 11:49

(Edited to provide a few more \vdots instructions, per the OP's updated request)

Instead of using an aligned environment, I would use a basic array environment to align the various parts of the equation. This way, it's straightforward to align all + and = symbols as well as the remaining constituent parts of the system of equations. Observe also the four \vdots instructions in the third row.

\documentclass{article}
\usepackage{array}
\begin{document}
$$\label{eq:secular} \setlength\arraycolsep{0pt} \renewcommand\arraystretch{1.25} \begin{array}{*{4}{c >{{}}c<{{}}} c} (\mathcal{H}_{11}- S_{11}E_i)c_{1i} & + & (\mathcal{H}_{12}- S_{12}E_i)c_{2i} & + & \cdots & + & (\mathcal{H}_{1n}- S_{1n}E_i)c_{ni} & = & 0\\ (\mathcal{H}_{21}- S_{21}E_i)c_{1i} & + & (\mathcal{H}_{22}- S_{22}E_i)c_{2i} & + & \cdots & + & (\mathcal{H}_{2n}- S_{2n}E_i)c_{ni}& = & 0\\ \vdots & & \vdots & & \vdots & & \vdots & & \\ (\mathcal{H}_{n1}- S_{n1}E_i)c_{ni}& + & (\mathcal{H}_{n2}- S_{n2}E_i)c_{2i}& + & \cdots& + & (\mathcal{H}_{nn}- S_{nn}E_i)c_{ni}& = & 0 \\ \end{array}$$
\end{document}


You can do it with alignedat with a couple of tricks.

1. I locally define \2 to provide a double index as wide as nn so the alignment will be automatic between the variables; the \2 macro will only be available in that equation environment.

2. I use the low level instruction \multispan to insert a row of dots.

Full code

\documentclass{article}
\usepackage{amsmath,calc}

\begin{document}

\label{eq:secular} \newcommand{\2}[1]{% _{\makebox[\widthof{\scriptstyle nn}][l]{\scriptstyle #1}}% } \begin{alignedat}{4} (\mathcal{H}\2{11}- S\2{11}E_i)c\2{1i} &+(\mathcal{H}\2{12}-S\2{12}E_i)c\2{2i} &&+\dotsb &&+(\mathcal{H}\2{1n}-S\2{1n}E_i)c\2{ni} &&=0\\ (\mathcal{H}\2{21}-S\2{21}E_i)c\2{1i} &+(\mathcal{H}\2{22}-S\2{22}E_i)c\2{2i} &&+\dotsb &&+(\mathcal{H}\2{2n}-S\2{2n}E_i)c\2{ni} &&=0\\ \multispan{8}{\dotfill}\\[1ex] %&\dotsb&\dotsb&\dotsb&\dotsb\\ (\mathcal{H}\2{n1}-S\2{n1}E_i)c\2{ni} &+(\mathcal{H}\2{n2}-S\2{n2}E_i)c\2{2i} &&+\dotsb &&+(\mathcal{H}\2{nn}-S\2{nn}E_i)c\2{ni} &&=0 \end{alignedat}

\end{document}


You also can do that with the alignedat environment. I propose two codes: the first aligns the + and = signs, and the first —, the second aligns all signs, at the cost of some slightly distorted space:

         \documentclass[a4paper, 11pt]{book}
\usepackage[utf8]{inputenc}
\usepackage{fourier, erewhon}

\usepackage{mathtools}

\begin{document}

\begin{alignedat}{4} (\mathcal{H}_{11}&-S_{11}E_i)c_{1i} & & +(\mathcal{H}_{12} -S_{12}E_i)c_{2i} & + \cdots & +(\mathcal{H}_{1n} - S_{1n}E_i)c_{ni} & =0\\ (\mathcal{H}_{21}&-S_{21}E_i)c_{1i} & & +(\mathcal{H}_{22}-S_{22}E_i)c_{2i} & + \cdots & +(\mathcal{H}_{2n}- S_{2n}E_i)c_{ni} & =0\\ % &\cdots&\cdots&\cdots&\cdots\\ (\mathcal{H}_{n1}&-S_{n1}E_i)c_{ni} & & +(\mathcal{H}_{n2}-S_{n2}E_i)c_{2i} & +\cdots & +(\mathcal{H}_{nn} - S_{nn}E_i)c_{ni} &= 0 \label{eq:secular} \end{alignedat}

\begin{alignedat}{6} (\mathcal{H}_{11} & -S_{11}E_i)c_{1i} & & {} +(\mathcal{H}_{12} & & {}-S_{12}E_i)c_{2i} &{} + \cdots & +(\mathcal{H}_{1n} && {} - S_{1n}E_i)c_{ni} & =0\\ (\mathcal{H}_{21} & -S_{21}E_i)c_{1i} & & {} +(\mathcal{H}_{22}& & {}-S_{22}E_i)c_{2i} &{} + \cdots & +(\mathcal{H}_{2n} && {} - S_{2n}E_i)c_{ni} & =0\\ % &\cdots&\cdots&\cdots&\cdots\\ (\mathcal{H}_{n1} & -S_{n1}E_i)c_{ni} & & {} +(\mathcal{H}_{n2}& & {}-S_{n2}E_i)c_{2i} &{} + \cdots & +(\mathcal{H}_{nn} && {} - S_{nn}E_i)c_{ni} &= 0 \label{eq:secular} \end{alignedat}

\end{document}


• You have two unnecessary trailing \\. – Manuel Apr 9 '16 at 19:35
• Oh! yes. They come from the O.P.'s post. Thanks for pointing it. – Bernard Apr 9 '16 at 19:50