14

I find that I have unpleasant spacing between the equals sign and (e.g.) the exponential function in this particular case, while using the align environment. I have a long expression which has to be split up in multiple rows. The alignment character & appears to gobble up all space when it comes after the equals sign. How could I remedy this while still preserving the plus sign alignment below?

Ideally, I would like to have the second row from the first equation, and the first row from the second equation.

Compiled document

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{align} % bad spacing at first row, but correctly placed second row
    2 \cosh t =& e^t \\
            &+ e^{-t} 
\end{align}
\begin{align} % good spacing at first row, but incorrectly placed second row
    2\cosh t &= e^t \\
            &+ e^{-t} 
\end{align}
\end{document}
  • 2
    Welcome to TeX.SE! To get the correct spacing around the = sign, one must write &= rather than =&. – Mico Nov 17 '14 at 13:50
7

Put the ampersand before the equals sign. Then use \quad to create the indentation in the second row.

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{align}                                                                   
    2 \cosh t &= e^t \\                                                         
              &\quad+ e^{-t}                                                    
\end{align}
\end{document}

You can also use \hspace if you want a different length for the indentation.

alignment

  • 4
    Wouldn't \begin{align} 2 \cosh t &= e^t \\ &\phantom{{}={}} + e^{-t} \end{align} be better? Then the plus symbol would be inset by the width of the equals sign, with the correct spacing. – Niel de Beaudrap Nov 17 '14 at 17:21
  • I'd say it's a matter of taste. – Ian Thompson Nov 18 '14 at 8:08
  • @Niel de Beaudrap: You are missing a \negmedspace for correct spacing: 2 \cosh t &= e^t \\ &\phantom{{}={}} \negmedspace + e^{-t} – Christoph Apr 6 at 6:42
7

I wouldn't try aligning the plus with e^t, but if you insist, here's how.

\documentclass{article}
\usepackage{amsmath}
\begin{document}

\noindent
The plus is flush with $e^t$ (I wouldn't recommend it):
\begin{align}
2\cosh t ={}& e^t \\
            & \negmedspace+ e^{-t}
\end{align}
The plus is moved right (better):
\begin{align}
2\cosh t &= e^t \\
         &\qquad+ e^{-t}
\end{align}
\end{document}

With \negmedspace we kill the space at the left of the binary operation symbol.

enter image description here

However, align is the wrong tool here:

\documentclass{article}
\usepackage{amsmath}
\begin{document}

\begin{equation}
\begin{split}
2\cosh t &= e^t \\
         &\qquad + e^{-t}
\end{split}
\end{equation}

enter image description here

5

Suppose you wish to ensure that the two instances of e are aligned vertically, while respecting the fact that a binary operator (+) precedes the e in the second row. The most direct way to obtain this type of alignment is to use a pair of \hphantom ("horizonal phantom") statements. The one in the first row mimics the + symbol (a binary operator) from the second row, and the \hphantom statement in the second row mimics the = symbol (a relational operator) from the first row. The {} pairs are there to help TeX figure out which type of operator applies.

enter image description here

\documentclass{article}
\usepackage{amsmath}
\setlength\textwidth{3in} %% just for this example
\begin{document}
\begin{align}
    2\cosh t &= \phantom{{}+{}} \mathrm{e}^t \\
             &\phantom{{}={}} + \mathrm{e}^{-t}
\end{align}
\end{document} 
3

You have placed the & wrong; it should go before the equal sign to get the correct spacing. Also, I've used \hphantom to indent the expression in the second line to get the correct alignment. (Notice the {} before =.)

\documentclass{article}

\usepackage{amsmath}

\begin{document}

\begin{align}
   2\cosh t
   &= e^{t} \\
   &\hphantom{{}=} + e^{-t} 
\end{align}

\end{document}

output

  • 1
    It is not wrong, one just have to be a bit more careful. Besides ` = {} &` is a lot short to type than &\hphantom{{}=} ;-) – daleif Nov 17 '14 at 15:19
  • @daleif Good point. The reason why I used \hphantom is that it's more 'universal'. – Svend Tveskæg Nov 17 '14 at 16:33
2

Strictly speaking, only the first part of egreg's answer and Niel de Beaudrap's modified comment solve the problem as intended by Martin L. All other answers require space corrections of at least 1 or 2 mu. Here is an alternative.

LaTeX generically encloses relation symbols with thick spaces \;, and binary symbols with medium spaces \:. The symbols = and + in our example are respectively of these kinds. Therefore, downgrading them to ordinary symbols, what we want is:

2 \cosh t & \; \mathord{=} \; e^t \\
          & \; \phantom{=} \; \mathord{+} \: e^{-t}

A practical incarnation of the above is (see page 36 of l2kurz.pdf):

2 \cosh t & = e^{t} \\
          & \mathrel{\phantom{=}} \negmedspace {} + e^{-t}

First, we redeem the relation status of = robbed by the \phantom command. Second, we insert an empty math atom {} telling LaTeX to interpret + as a binary rather than a prefix symbol; but this creates a spurious medium space \: that needs to be compensated.

enter image description here

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