[Tex/LaTex] How to combine paragraphs of text with equations using \shortintertext and ‘align’

alignequationsline-spacingmathtoolsparagraphs

I commented that I'm solving problems to make a book of basic math (or precalculus).
In the environment or region of solving an exercise I want to combine paragraphs of text (using \shortintertext) with equations which I can align with respect to any sign of equality or inequality (align environment). I wish I could list some of these equations. And most importantly, I want to control the line spacing in this development environment. You can see that the following code

\documentclass{article}
\usepackage{showframe}
\usepackage{mathtools}
\usepackage{amsthm}
\begin{document}

\begin{align*}
\shortintertext{The equation is..}
4x &= 3x + 3&&(1)\\
\shortintertext{then by t2 and t7 theorems have..}
\left(3x+3\leq 4x <x+4\right) & &&(2)\\
\shortintertext{..respectively}
\end{align*}

\end{document}

will produce this document in DVI in which the numbering of formulas (or equations) are not close to the right margin. I want these numbers (within the parenthesis) are located very close to the right margin.
$screenshot 01 - line spacing with \begin{align}$

To control the line spacing I tried with commands like \addtolength{\jot}{2em}

\begingroup
\addtolength{\jot}{2em}
\begin{align*}
\shortintertext{The equation is..}\\[0.1em]
4x &= 3x + 3&&(1)\\
\shortintertext{then by t2 and t7 theorems have..}\\[0.1em]
\left(3x+3\leq 4x <x+4\right) & &&(2)\\
\shortintertext{..respectively}
\end{align*}
\endgroup

and becomes chaotic:
enter image description here

Can you solve or should I choose other environments?

Thanks in advance.

Best Answer

You should let the align environment handle the numbering for you. Then the numbers will appear close to the right margin and the equations will be centered correctly.

\documentclass{article}
\usepackage{showframe}
\usepackage{mathtools}

\begin{document}

The equation is
\begin{align}
4x &= 3x + 3.\\
\shortintertext{Then we have}
3x+3&\leq 4x <x+4.
\end{align}

\end{document}

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I would definitely go the second way with $\displaystyle: I find that it looks strange to have something centered after a bullet. To get the vertical alignment correct, just add [t] after \begin{aligned}, where "t" means "top". (See also the top of page 8 of the User's guide for the amsmath Package.)

[Tex/LaTex] Labeled linear program with labeled equations and wide objective function

I've taken some liberties in interpreting what you're trying to accomplish here. For example, I assume that you will manually create the tag names for the LP blocks. Also, I think my solution lacks a certain elegance: in particular, each such block has to be created separately. I don't really like that.

Here's the general idea: create two adjacent boxes centered on the baseline with one containing a dummy equation to create the label for the entire block. Spacing after the boxes is a bit wonky. So, I add ~ after the last flalign environment. (Short coming: you also have to manually adjust the width of the first parbox to get the label to be positioned correctly.)

You seemed to want the first line to somehow align with the LP. I've got two solutions to that. The first puts the first line into a box of zero width. (Short coming: you have to re-enter math mode within this box.) The second puts this first line in its own flalign environment. (Short coming: you have to adjust the vertical spacing between the two environments.)

\documentclass{article}
\usepackage{amsmath,calc}
\newlength{\LPlhbox}
\begin{document}


\settowidth{\LPlhbox}{(P.1)}%
\noindent%
\parbox{\LPlhbox}{\begin{align}
               \tag{P.1}\label{My first LP Block}
               \end{align}}%
\hspace*{\fill}%
\begin{minipage}{\linewidth-2cm}
    \begin{flalign}\notag
     & \makebox[0pt][l]{$\displaystyle{}\max \sum\limits_{v \in V} x_v + \sum\limits_{e \in E} y_e + 10000\gamma$} \\
    \label{this line can be referenced}
     & \text{s.t.} & x_v + x_w   & \geq  0                 && \forall \{v,w\} \in E && \\
     &             & y_3         & \geq 0                  && \forall e\in E        && \\
     &             & (\delta(U)) & \geq \frac{1}{2}(|U|-1) && \forall U \subseteq V
    \end{flalign}~
\end{minipage}

\settowidth{\LPlhbox}{(P.2)}%
\noindent%
\parbox{\LPlhbox}{\begin{align}
               \tag{P.2}\label{My second LP Block}
               \end{align}}%
\hspace*{\fill}%
\begin{minipage}{\linewidth-2cm}
   \begin{flalign}\notag
     \max \sum\limits_{v \in V} x_v + \sum\limits_{e \in E} y_e + 10000\gamma &&
   \end{flalign}
    \vspace{-1.5\baselineskip}
   \begin{flalign}
    & \text{s.t.} & x_v + x_w   & \geq  0                 && \forall \{v,w\} \in E && \\
    &             & y_3         & \geq 0                  && \forall e\in E        && \\
    &             & (\delta(U)) & \geq \frac{1}{2}(|U|-1) && \forall U \subseteq V
   \end{flalign}~
\end{minipage}

Notice that we can reference line~\ref{this line can be referenced}
and both block~\ref{My first LP Block} and block~\ref{My second LP Block}
\end{document}

What would be nice is if there were a commands \lefttag and \righttag to temporarily override document defaults.

You can also easily create a command to do the work of the left-hand box.

\newcommand{\LPblocktag}[2]{\settowidth{\LPlhbox}{(#1)}%
                            \parbox{\LPlhbox}{\begin{align}\tag{#1}#2\end{align}}%
                            \hspace*{\fill}}

I've written the second argument as I have because I don't want to assume you'll be referencing every such block.

So the first block above can be written as

\noindent%
\LPblocktag{P.3}{\label{My third LP Block}}%
\begin{minipage}{\linewidth-2cm}
    \begin{flalign}\notag
     & \makebox[0pt][l]{$\displaystyle{}\max \sum\limits_{v \in V} x_v + \sum\limits_{e \in E} y_e + 10000\gamma$} \\
    \label{this line can be referenced}
     & \text{s.t.} & x_v + x_w   & \geq  0                 && \forall \{v,w\} \in E && \\
     &             & y_3         & \geq 0                  && \forall e\in E        && \\
     &             & (\delta(U)) & \geq \frac{1}{2}(|U|-1) && \forall U \subseteq V
    \end{flalign}~
\end{minipage}

I can reference \ref{My third LP Block}

enter image description here

Best Answer

Related Solutions

[Tex/LaTex] aligning a multiline formula with the bullet of itemize

[Tex/LaTex] Labeled linear program with labeled equations and wide objective function

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