3

New user of LaTeX here. While learning how to align equations with the equation and split environments, I asked myself how I could modify the vertical alignment in a single split expression. Here is what I have :

\begin{equation*}
    \begin{split}
        & w = u - v \\
        \iff & w_n = u_n - v_n \\
        \iff & w_{n+1} = u_{n+1} - v_{n+1} \\
        &= 2u_n - n + 3 - (2v_n - n + 3) \\
        &= 2u_n - n + 3 - 2v_n + n - 3 \\
        &= 2u_n - 2v_n \\
        &= 2(u_n - v_n) \\
        &= 2w_n
    \end{split}
\end{equation*}

and what it produces :

result of tried code

What I would like to have is this :

wanted result

How would I manage to do so?

1
  • 1
    Welcome to TeX.SE.
    – Mico
    Sep 26 at 18:37
8

Nest aligned (top aligned) in align*. No phantom or zero width boxes are needed.

Explanation: you have one global alignment point (at the w's), plus alignment for a whole block at =.

\documentclass{article}
\usepackage{amsmath}

\begin{document}

\begin{align*}
& w = u - v \\
\Longleftrightarrow\quad
& w_n = u_n - v_n \\
\Longleftrightarrow\quad
& \begin{aligned}[t]
  w_{n+1} &= u_{n+1} - v_{n+1} \\
          &= 2u_n - n + 3 - (2v_n - n + 3) \\
          &= 2u_n - n + 3 - 2v_n + n - 3 \\
          &= 2u_n - 2v_n \\
          &= 2(u_n - v_n) \\
          &= 2w_n
  \end{aligned}
\end{align*}

\end{document}

Don't use \iff here, it adds space also at its left side.

enter image description here

7

I suggest you replace the single split environment with two consecutive aligned environments.

enter image description here

\documentclass{article}
\usepackage{array}
\usepackage{mathtools} % for '\mathrlap' macro
\begin{document}

\begin{equation*}
    \begin{aligned}[b]
               & w      \mathrlap{{}= u - v}     \\
        \iff{} & w_n    \mathrlap{{}= u_n - v_n} \\
        \iff{} & w_{n+1}
        \end{aligned}%
        \begin{aligned}[t]
        &= u_{n+1} - v_{n+1} \\
        &= 2u_n - n + 3 - (2v_n - n + 3) \\
        &= 2u_n - n + 3 - 2v_n + n - 3 \\
        &= 2u_n - 2v_n \\
        &= 2(u_n - v_n) \\
        &= 2w_n
    \end{aligned}
\end{equation*}

\end{document}

Instead of using two aligned environments, one could also employ a two-column array environment to generate the screenshot shown above.

\[
\newcolumntype{L}{>{\displaystyle}l} % \newcolumntype is defined in 'array' package
\setlength\arraycolsep{0pt}
\renewcommand{\arraystretch}{1.25} % mimic look of displaymath env.
\begin{array}{LL}
\multicolumn{2}{L}{\phantom{\iff{}} w = u - v}  \\
\multicolumn{2}{L}{\iff w_n = u_n - v_n}        \\
\iff w_{n+1} &{}= u_{n+1} - v_{n+1}             \\
             &{}= 2u_n - n + 3 - (2v_n - n + 3) \\
             &{}= 2u_n - n + 3 - 2v_n + n - 3   \\
             &{}= 2u_n - 2v_n                   \\
             &{}= 2(u_n - v_n)                  \\
             &{}= 2w_n
\end{array}
\]
2
  • 1
    Thanks for this solution! While I understand most of the code, I don't know what mathrlap is, and I could barely find it on the internet. Could you explain it to me or refer me to an explanation please? Sep 26 at 19:36
  • 1
    @LucasMartiniano - \mathrlap is a macro that's provided by the mathtools package. See section 3.1, "Fine-tuning mathematical layout", of the package's user guide for a discussion of the \mathclap, \mathllap, and mathrlap macros.
    – Mico
    Sep 26 at 19:51
2

Welcome to TeX:SE!

For showed equations layout the split is not appropriate. With use of the array you can get the following result:

enter image description here

\documentclass{article}
\usepackage{amsmath}

\begin{document}
\[\setlength\arraycolsep{1pt}
    \begin{array}{r r l}
     &   w =    & u - v       \\
\iff & w_n =    & u_n - v_n   \\
\iff & w_{n+1}  & = u_{n+1} - v_{n+1}   \\
     &          & = 2u_n - n + 3 - (2v_n - n + 3)   \\
     &          & = 2u_n - n + 3 - 2v_n + n - 3     \\
     &          & = 2u_n - 2v_n         \\
     &          & = 2(u_n - v_n)        \\
     &          & = 2w_n
    \end{array}
\]
\end{document}
2
  • I think the OP would like to align the first three rows so that the w terms line up.
    – Mico
    Sep 26 at 18:55
  • @Mico, you may be right, but to my taste suggested solution gives nicer result ;-) (very opinion based).
    – Zarko
    Sep 26 at 19:00

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