Alignment in enumerate

Question

I want to write something like:

\begin{enumerate}
  \item $f(x)=0\quad,\quad\forall{x}\in{S_1}$
  \item $g(x)=0\quad,\quad\forall{x}\in{S_2}}$
\end{enumerate}

and I want each line to be aligned at the comma (between the \quads). Is there any simple way to do this?

Because the above example was too simple, I present a part of the actual code:

\begin{enumerate}
\item 
$X\left(V\left(\varphi\right)\right)=\left\langle {{\operatorname{grad}}_{V}}\left(\varphi\right),X\left(\varphi\right)\right\rangle\quad,\quad\forall{X}\in{TM},\varphi\in{{C}^{\infty}}\left(M,W\right)$
\item ${{\operatorname{grad}}_{V}}\left(\rho\left(g\right)u\right)=\rho\left(g\right){{\operatorname{grad}}_{V}}\left(u\right)\quad,\quad\forall{u}\in{W},g\in{G}$
\item $\left\langle{\operatorname{grad}}_{V}\left(u\right),\rho_{*}\left(X\right)u\right\rangle=0\quad\quad\quad\quad\,,\quad\forall{u}\in{W},X\in{\mathfrak{g}}$
\end{enumerate}

As you can see I have "manually" aligned the commata, by inserting spaces with the appropriate length. Is there a simple way to align them automatically?

Welcome to TeX.SX! Do you explicitly need them to be inside an enumerate environment? If you're not familiar you should definitely take a look at what amsmath and the likes of the align environment which it provides. Possibly you want to look at Sharing alignment between equations in two different items. — Dai Bowen, Dec 02 '16 at 15:19

Werner · Accepted Answer · 2016-12-04T02:31:29.397

Here are two ways of achieving this:

\documentclass{article}

\usepackage{mathtools,eqparbox}

\begin{document}

\begin{enumerate}
  \item $f(x) = 0, \quad \forall x \in S_1$
  \item $g(x) = 0, \quad \forall x \in S_2$

  \bigskip

  \item $f(x) = 0, \quad \forall x \in S_1$
  \item $\phantom{f(x)}\mathllap{g(x)} = 0, \quad \forall x \in S_2$

  \bigskip

  \item $\eqmakebox[lhs]{$f(x)$} = 0, \quad \forall x \in S_1$
  \item $\eqmakebox[lhs][r]{$g(x)$} = 0, \quad \forall x \in S_2$
\end{enumerate}

\end{document}

(1) and (2) above is your original setup. We notice that f(x) is wider than g(x). As such, our focus will be only on moving g(x) to the right a smidge.

In (4) we insert a \phantom{f(x)} which puts us in the correct horizontal position, then insert g(x) in a math box with a left overlap (or \mathllap).

In (6) we insert both f(x) and g(x) inside an \eqmakebox with the same label (lhs). This ensures that they will take up the same space horizontally. Furthermore, we align g(x) to the r within the box.

Here is a more complex example using the same setup:

\documentclass{article}

\usepackage{mathtools,amsfonts,eqparbox}

\DeclareMathOperator{\grad}{grad}

\begin{document}

% Original setup
\begin{enumerate}
  \item 
  $X\left(V\left(\varphi\right)\right)=\left\langle {{\operatorname{grad}}_{V}}\left(\varphi\right),X\left(\varphi\right)\right\rangle\quad,\quad\forall{X}\in{TM},\varphi\in{{C}^{\infty}}\left(M,W\right)$
  \item ${{\operatorname{grad}}_{V}}\left(\rho\left(g\right)u\right)=\rho\left(g\right){{\operatorname{grad}}_{V}}\left(u\right)\quad,\quad\forall{u}\in{W},g\in{G}$
  \item $\left\langle{\operatorname{grad}}_{V}\left(u\right),\rho_{*}\left(X\right)u\right\rangle=0\quad\quad\quad\quad\,,\quad\forall{u}\in{W},X\in{\mathfrak{g}}$
\end{enumerate}

\bigskip

\begin{enumerate}
  \item
  $\phantom{\grad_V(\rho(g) u) = \rho(g) \grad_V(u)}
   \mathllap{X(V(\varphi)) = \langle \grad_V(\varphi), X(\varphi) \rangle}, \quad \forall X \in TM , \varphi \in C^\infty(M,W)$

  \item
  $\grad_V(\rho(g) u) = \rho(g) \grad_V(u), \quad \forall u \in W ,g \in G $

  \item
  $\phantom{\grad_V(\rho(g) u) = \rho(g) \grad_V(u)}
   \mathllap{\langle \grad_V(u), \rho_*(X) u \rangle = 0}, \quad \forall u \in W , X \in \mathfrak{g}$
\end{enumerate}

\bigskip

\begin{enumerate}
  \item
  \eqmakebox[lhs][r]{$X(V(\varphi)) = \langle \grad_V(\varphi), X(\varphi) \rangle$}%
  $, \quad \forall X \in TM , \varphi \in C^\infty(M,W)$

  \item
  \eqmakebox[lhs]{$\grad_V(\rho(g) u) = \rho(g) \grad_V(u)$}%
  $, \quad \forall u \in W ,g \in G $

  \item
  \eqmakebox[lhs][r]{$\langle \grad_V(u), \rho_*(X) u \rangle = 0$}%
  $, \quad \forall u \in W , X \in \mathfrak{g}$
\end{enumerate}

\end{document}

It works pretty well with my simple example but when I put in the real expressions (I also used [rhs]) the result didn't look that good. Is there any way to align at the commas, without using equation boxes? — user3257624, Dec 03 '16 at 14:47
@user3257624: There are many ways. Perhaps providing something that is a bit more relevant to your use-case would also help in guiding you. Please provide the community with a minimal working example (MWE) that shows us what you're talking about. — Werner, Dec 03 '16 at 16:45
I have added to my original post part of the code I want to align — user3257624, Dec 03 '16 at 18:15
@user3257624: I've added your code to show how to achieve the alignment. Note how I've simplified the code, dropping most of your \left...\right combinations. — Werner, Dec 04 '16 at 02:32
although I aligned the equation boxes on the left and added an extra quad before the comma, in order to produce the desired result — user3257624, Dec 04 '16 at 16:29
@user3257624: True; that's how you like things. I was somewhat suggestive in the way I would like things by not using \quad , \quad. You understand the approach though, which is essentially what I tried to convey. — Werner, Dec 04 '16 at 17:15

score 2 · Answer 2 · answered Dec 02 '16 at 15:20

Use the align environment from the amsmath package.

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{align}
   f(x)&=0\qquad\text{for all $x\in S_1$} \label{eq:f}\\
   g(x)&=0\qquad\text{for all $x\in S_2$} \label{eq:g}
\end{align}
See equations \ref{eq:f} and~\ref{eq:g}.
\end{document}

To have the numbers at the left margin, use the leqno option as a class option

\documentclass[leqno]{article}

or as a package option

\usepackage[leqno]{amsmath}

Alignment in enumerate

2 Answers2