19

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}
Martin L
  • 293

5 Answers5

11

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

Ian Thompson
  • 43,767
10

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

egreg
  • 1,121,712
5

You have placed the & in an odd position, I think; it's "smarter" to put it in front of 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

Svend Tveskæg
  • 31,033
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}
Mico
  • 506,678
5

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 encloses relation symbols in thick spaces \; and binary operator symbols in medium spaces \:. The symbols = and + in our example are each of this type. 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} \\
          & \phantom{=} \  + e^{-t}

The \phantom command strips = of its relation status, leaving it short of two thick spaces. On the other hand, LaTeX interprets + as a binary operator, creating a spurious medium space. So we need an extra normal space: \ = \; + \; - \:.

enter image description here

Christoph
  • 63