# How to align left and indent all but the first line in a mult-line equation?

I'm trying without luck to break an equation in a two-column document, such that the 1st line is aligned to the left, and all the other lines are indented and aligned among themselves at two points. So far the closest I've gotten is the cheat shown below, using 2 align environments. How can I properly accomplish this?

Also, how can I reduce the space between the 1st and end 2nd alignment points (e.g. before the "+" sign in the last line of the equation)? Ideally, I'd like to make the equation number fit in the last line.

Thanks and regards, Jorge.

\documentclass[twocolumn]{article}
\usepackage{amsmath}
\usepackage{showframe}
\usepackage{etoolbox}
\newlength\Fcolumnseprule
\setlength\Fcolumnseprule{0.4pt}
\makeatletter
\newcommand\ShowInterColumnFrame{
\patchcmd{\@outputdblcol}
{{\normalcolor\vrule \@width\columnseprule}}
{\vrule \@width\Fcolumnseprule\hfil
{\normalcolor\vrule \@width\columnseprule}
\hfil\vrule \@width\Fcolumnseprule
}{}{}}
\makeatother
\ShowInterColumnFrame

\begin{document}

\noindent{}This kind of works:

\begin{flalign*}
&V_{R}\cdot\overline{B}_{rec}&\notag\\
\end{flalign*}
\vspace{-30pt}
\begin{flalign}
&&&=V_{R}\cdot\overline{B}_{f}&&{+}\left(V_{R}\cdot\overline{B}_{b}\right)/A_{rec} &\notag\\
&&&=v_{IN}+q_{n,f}&&{+}\frac{\Sigma_{i}a_{i}(-q_{n,f})^{i}+q_{n,b}}{A_{rec}} &\notag\\
&&&=v_{IN}+\left(1{-}\frac{a_{1}}{A_{rec}}\right)q_{n,f}&&{+}\frac{\Sigma_{i\neq{}1}a_{i}(-q_{n,f})^{i}+q_{n,b}}{A_{rec}} &
\end{flalign}

\noindent{}This definitely doesn't:

\begin{flalign}
V_{R}\cdot\overline{B}_{rec}\notag\\
&=V_{R}\cdot\overline{B}_{f}&&{+}\left(V_{R}\cdot\overline{B}_{b}\right)/A_{rec} &\notag\\
&=v_{IN}+q_{n,f}&&{+}\frac{\Sigma_{i}a_{i}(-q_{n,f})^{i}+q_{n,b}}{A_{rec}} &\notag\\
&=v_{IN}+\left(1{-}\frac{a_{1}}{A_{rec}}\right)q_{n,f}&&{+}\frac{\Sigma_{i\neq{}1}a_{i}(-q_{n,f})^{i}+q_{n,b}}{A_{rec}} &
\end{flalign}

\end{document}


Result:

(1) Thanks so much everyone for your replies; it's clear now that this is best achieved with other environments besides \align.

(2) After pluging egreg's solution in my actual document code (which uses the ieeetran class), the equation number appears centered vertically to it (see below)... any ideas on how to force it to appear aligned to the bottom of the equation?

Possibly you're looking for \lefteqn (that hides the width) and alignedat:

\documentclass[twocolumn]{article}
\usepackage{amsmath}

%% just for the example
\usepackage{showframe}
\usepackage{etoolbox}
\newlength\Fcolumnseprule
\setlength\Fcolumnseprule{0.4pt}
\makeatletter
\newcommand\ShowInterColumnFrame{
\patchcmd{\@outputdblcol}
{{\normalcolor\vrule \@width\columnseprule}}
{\vrule \@width\Fcolumnseprule\hfil
{\normalcolor\vrule \@width\columnseprule}
\hfil\vrule \@width\Fcolumnseprule
}{}{}}
\makeatother
\ShowInterColumnFrame
%%

\begin{document}

This should be what you want; remember not leaving
blank lines before displays:
\begin{alignedat}{2} \lefteqn{V_{R}\cdot\overline{B}_{\mathrm{rec}}}\;\;\\ &=V_{R}\cdot\overline{B}_{f} &&+\left(V_{R}\cdot\overline{B}_{b}\right)/A_{\mathrm{rec}}\\ &=v_{IN}+q_{n,f} &&+\frac{\sum_{i}a_{i}(-q_{n,f})^{i}+q_{n,b}}{A_{\mathrm{rec}}}\\ &=v_{IN}+\left(1{-}\frac{a_{1}}{A_{\mathrm{rec}}}\right)q_{n,f} &&+\frac{\sum_{i\neq{}1}a_{i}(-q_{n,f})^{i}+q_{n,b}}{A_{\mathrm{rec}}} \end{alignedat}

\end{document}


I changed all rec subscripts in \mathrm{rec} and \Sigma to \sum, that seems more appropriate.

If you want to force the number to be at the bottom line when it fits the display, use \begin{aligned}[b]{2}:

\documentclass{IEEEtran}
\usepackage{amsmath}
\usepackage{newtxtext,newtxmath}

\usepackage{lipsum}

\begin{document}

This should be what you want; remember not leaving
blank lines before displays:
\begin{alignedat}[b]{2} \lefteqn{V_{R}\cdot\overline{B}_{\mathrm{rec}}}\;\;\\ &=V_{R}\cdot\overline{B}_{f} &&+\left(V_{R}\cdot\overline{B}_{b}\right)/A_{\mathrm{rec}}\\ &=v_{IN}+q_{n,f} &&+\frac{\sum_{i}a_{i}(-q_{n,f})^{i}+q_{n,b}}{A_{\mathrm{rec}}}\\ &=v_{IN}+\left(1{-}\frac{a_{1}}{A_{\mathrm{rec}}}\right)q_{n,f} &&+\frac{\sum_{i\neq{}1}a_{i}(-q_{n,f})^{i}+q_{n,b}}{A_{\mathrm{rec}}} \end{alignedat}
\lipsum

\end{document}


• Thanks so much egreg! It mostly works fine, but when I plug it in my actual document, the equation numbering appears centered vertically with the equation, instead that at the bottom (see below). Any ideas on how I could force the numbering position? – dontpanic Oct 13 '17 at 22:13
• @dontpanic \begin{alignedat}[b]{2} I added the example. – egreg Oct 13 '17 at 22:24
• Great! Thanks so much again! I tried googling to find information on how to use alignedat, but found nothing. Do you now where I can learn more about it? – dontpanic Oct 13 '17 at 22:35
• @dontpanic texdoc amsmath; but it's essentially the same as alignat as far as syntax and output is concerned, but it's the “inner” variant, just like aligned is of align. – egreg Oct 13 '17 at 22:54
• I've typically used \mathrlap{...}\quad instead of \lefteqn{…}\;\;; should I prefer \lefteqn, presuming that I'm using mathtools anyway? – wchargin Oct 14 '17 at 1:17

With a similar approach like yours but with less &s you could create something like the following:

\documentclass[twocolumn]{article}

\usepackage{amsmath,showframe,etoolbox}
\newlength\Fcolumnseprule
\setlength\Fcolumnseprule{0.4pt}
\makeatletter
\newcommand\ShowInterColumnFrame{
\patchcmd{\@outputdblcol}
{{\normalcolor\vrule \@width\columnseprule}}
{\vrule \@width\Fcolumnseprule\hfil
{\normalcolor\vrule \@width\columnseprule}
\hfil\vrule \@width\Fcolumnseprule
}{}{}}
\makeatother
\ShowInterColumnFrame

\begin{document}
\noindent
This works but might lead to problems:
\begin{flalign}
V_R \cdot \overline{B}_\mathrm{rec}\hspace{-3.5em}&\notag\\
& = V_{R}\cdot\overline{B}_{f}
&&+ \left(V_{R}\cdot\overline{B}_{b}\right)/A_\mathrm{rec}\notag\\
& = v_{IN}+q_{n,f}
&&+\frac{\Sigma_{i}a_{i}(-q_{n,f})^{i}+q_{n,b}}{A_\mathrm{rec}}\notag\\
& = v_{IN}+\left(1{-}\frac{a_{1}}{A_\mathrm{rec}}\right)q_{n,f}
&&+\frac{\Sigma_{i\neq{}1}a_{i}(-q_{n,f})^{i}+q_{n,b}}{A_\mathrm{rec}}
\end{flalign}
\end{document}


note \sum not \Sigma which also allows the limits style which takes less horizontal space.

\documentclass[twocolumn]{article}
\usepackage{amsmath,mathtools}
\usepackage{showframe}
\usepackage{etoolbox}
\newlength\Fcolumnseprule
\setlength\Fcolumnseprule{0.4pt}
\makeatletter
\newcommand\ShowInterColumnFrame{
\patchcmd{\@outputdblcol}
{{\normalcolor\vrule \@width\columnseprule}}
{\vrule \@width\Fcolumnseprule\hfil
{\normalcolor\vrule \@width\columnseprule}
\hfil\vrule \@width\Fcolumnseprule
}{}{}}
\makeatother
\ShowInterColumnFrame

\begin{document}

This?
\begin{multlined} V_{R}\cdot\overline{B}_{\mathrm{rec}}\\ \,\begin{alignedat}{2} &=V_{R}\cdot\overline{B}_{f}&&+(V_{R}\cdot\overline{B}_{b})/A_{\mathrm{rec}} \\ &=v_{IN}+q_{n,f}&&+\dfrac{\sum\limits_{i}a_{i}(-q_{n,f})^{i}+q_{n,b}}{A_{\mathrm{rec}}} \\ &=v_{IN}+\bigl(1{-}\dfrac{a_{1}}{A_{\mathrm{rec}}}\bigr)q_{n,f}&&+\dfrac{\sum\limits_{i\neq{}1}a_{i}(-q_{n,f})^{i}+q_{n,b}}{A_{\mathrm{rec}}} \end{alignedat} \end{multlined}

\end{document}