[Tex/LaTex] To get one line of equation disregarded during the alignment process in align environment

alignamsmath

Couldn't find any answer to this question on anywhere. I have this one particular solution in my hands, which helps only if the equation to be disregarded for alignment is the first or the last of the array of equations, which is simply:

\documentclass{article}
\usepackage{amsmath}

\begin{document}
    \begin{gather} % or gather*
        2 + 5 + 123 + 45 = 175\\ % the equation I am taking out of alignment
        \begin{aligned}
             2 + 3 &= 5\\
            11 + 5 &= 16
        \end{aligned}
    \end{gather}
\end{document}

Which doesn't really look good to my eyes. Works though; works exactly as I hoped it to, and looks exactly as I wanted it to.

Then again, what would be the proper way to do it, which preferably also manages to deal with a not-aligned equation in between, rather than just at the beginning or the end? Heard and read about this ancient \noalign command, but also read that it is not supported or something like that.

Best Answer

You can use \mathclap from the mathtools package:

enter image description here

References:

TUGboat 2001: A complement to \smash, \llap, and\rlap -- Alexander R. Perlis.

Code:

\documentclass{article}
\usepackage{mathtools}

\begin{document}
\begin{align}
    \mathclap{2 + 5 + 123 + 45 = 175}\\ % the equation I am taking out of alignment
         2 + 3 &= 5\\
        11 + 5 &= 16
\end{align}
\end{document}

Related Solutions

[Tex/LaTex] Resetting alignment in the align environment

You can play around with columns to fool the alignment mechanism as:

\begin{align}
   \gamma_1 &= 8/15 &&& \gamma_2&= 5/12         &&& \gamma_3 &= 3/4 &\\
   \zeta_1  &= 0    &&& \zeta_2&= -17/60        &&& \zeta_3  &= -5/12& \\
   \beta_1  &= 4/15 &&& \beta_2&= 1/15          &&& \beta_3  &= 1/6&\\
     a_0 ={}&0      &&& a_1 = 8/15 && a_2 = 2/3 &&&\qquad a_3 = 1
\end{align}

enter image description here

but with all due respect, what you want to do, does not read well. I would have done something like the following

\begin{align}
   \gamma_1 &= 8/15 & \gamma_2&= 5/12  & \gamma_3 &= 3/4 \\
   \zeta_1  &= 0    & \zeta_2&= -17/60 & \zeta_3  &= -5/12 \\
   \beta_1  &= 4/15 & \beta_2&= 1/15   & \beta_3  &= 1/6\\
        a_0 &= 0    & a_1    &= 8/15   & a_2      &= 2/3 \\ \notag
            &       & a_3    &= 1      &          &
\end{align}

enter image description here

You can deliberately put some vertical space between the first three and the last to highlight the grouping effect which is, in my opinion, more important in order to convey the message rather than to be able to command a LaTeX array.

[Tex/LaTex] Label one line in align* environment

You can either \tag the line in an (unnumbered) align* or \nonumber each equation you don't want in a (numbered) align. Here's a snapshot of both:

enter image description here

\documentclass{article}
\usepackage{amsmath}% http://ctan.org/pkg/amsmath
\begin{document}
\begin{align*}
m_n^+ = \dfrac{1}{n}\sum\limits_{k=N+1}^{n} &= \dfrac{1}{n}\sum\limits_{k=N+1}^{n}\left(a_k-L+L\right) \\
                                            &< \dfrac{1}{n}\sum\limits_{k=N+1}^{n}\left(\dfrac{\epsilon}{2}+L\right) \\
                                            &< \dfrac{1}{n}\sum\limits_{k=1}^{n}\left(\dfrac{\epsilon}{2}+L\right) = \dfrac{\epsilon}{2}+L 
                                              \stepcounter{equation}\tag{\theequation}\label{myeq1}\\
\end{align*}
See~\eqref{myeq1}.

\begin{align}
m_n^+ = \dfrac{1}{n}\sum\limits_{k=N+1}^{n} &= \dfrac{1}{n}\sum\limits_{k=N+1}^{n}\left(a_k-L+L\right) \nonumber \\
                                            &< \dfrac{1}{n}\sum\limits_{k=N+1}^{n}\left(\dfrac{\epsilon}{2}+L\right) \nonumber \\
                                            &< \dfrac{1}{n}\sum\limits_{k=1}^{n}\left(\dfrac{\epsilon}{2}+L\right) = \dfrac{\epsilon}{2}+L \label{myeq2}
\end{align}
See~\eqref{myeq2}.
\end{document}

The approach depends on the ease of use, or perhaps the size (number/quantity) of the set of the equations.

The former \tag-method uses the same counter (equation), although it requires manually stepping. In both instances, \label works as usual to capture the number for later use through \eqref.

Best Answer

References:

Code:

Related Solutions

[Tex/LaTex] Resetting alignment in the align environment

[Tex/LaTex] Label one line in align* environment

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