# How can I decrease spaces between equations?

\documentclass[12pt,a4paper]{mwrep}
\renewcommand\baselinestretch{1.5}
\begin{document}
\chapter{Test}
Text text text text text text text text text text
$$1 + 2 + 3 = 6$$
Text text text text text text text text text text
$$1 + 2 + 3 = 6$$
$$1 + 2 + 3 = 6$$
\end{document}


Spaces between two equations and between equations and text are too big. How can I lower them? I know that using \renewcommand\baselinestretch{1.5} is responsible for that but I need this command.

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I would recommend the following measures:

(1) Instead of \renewcommand\baselinestretch{1.5}, load the setspace package with the nodisplayskipstretch option, and then execute the command setstretch{1.5} in your document's preamble:

...
\usepackage[nodisplayskipstretch]{setspace}
\setstretch{1.5}


This way, you won't experience the excessive spacing between lines of text and floating objects. Also, material in footnotes will remain single-spaced.

(2) When you have consecutive equations, don't use separate equation environments but instead use the gather environment provided by the amsmath package. (If the equations should be aligned along, say, their equal signs, use the align environment instead of the gather environment, using the ampersand, &, character as the alignment point.) Two consecutive equations would then be entered as

\begin{gather}
1 + 2 + 3 = 6 \\
2 + 4 + 6 = 12
\end{gather}

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\begin{gather} 1 + 2 + 3 = 6 \ 2 + 4 + 6 = 12 \end{gather} shows two equations in one line. –  Ichibann Oct 27 '11 at 19:52
Ok, I figured on my own that I need to put  \\  instead of  \  –  Ichibann Oct 27 '11 at 19:56
You need an & character on each line for an alignment tab. You can put it anywhere, but I ususally put it in front of the =. –  Brandon Kuczenski Oct 27 '11 at 20:03
It's not wrong to have two consecutive equation environments. However, doing so will in general use more space than if you use an environment that "knows" that successive lines are equations rather than switches between text and equations. Moreover, if you use consecutive equation environments, you can't align them on, say, the equal sign -- something you could do if you'd use the align environment, say. –  Mico Oct 27 '11 at 21:04
+1 for the gather environment. I didn't want to mess around with document-wide spacing parameters just because LaTeX didn't "know" I was providing a series of equations. –  Warrick Mar 23 '12 at 9:42

LaTeX uses \abovedisplayskip and \belowdisplayskip for the spacing above/below equations. There's also a short version of the former two commands for paragraphs ending/beginning with shorter lines. Here's an example showing the difference:

\documentclass{article}
\usepackage{amsmath}% http://ctan.org/pkg/amsmath
\begin{document}
Text text text text text text text text text text
$$1 + 2 + 3 = 6$$
Text text text text text text text text text text
\begin{align}
1 + 2 + 3 &= 6 \\
1 + 2 + 3 &= 6
\end{align}

\setlength{\belowdisplayskip}{0pt} \setlength{\belowdisplayshortskip}{0pt}
\setlength{\abovedisplayskip}{0pt} \setlength{\abovedisplayshortskip}{0pt}

Text text text text text text text text text text
$$1 + 2 + 3 = 6$$
Text text text text text text text text text text
\begin{align}
1 + 2 + 3 &= 6 \\
1 + 2 + 3 &= 6
\end{align}
\end{document}​


The same effect is obtained with/without a modified \baselinestretch - it is just clearer when viewed without that set. Of course, you can modify these lengths as needed.

Edit: Heed @egreg's suggestion and/or @Mico's answer regarding two equations

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One should never use two consecutive equation environment, but rather the gather environment provided by amsmath –  egreg Oct 27 '11 at 19:47

you should use package setspace for the vertical spacing. The distance between two equations is set by the short skips!

\documentclass[12pt,a4paper]{mwrep}
\usepackage{setspace}\onehalfspacing
\AtBeginDocument{%
}

\begin{document}
\chapter{Test}
Text text text text text text text text text text
$$1 + 2 + 3 = 6$$
Text text text text text text text text text text
$$1 + 2 + 3 = 6$$
$$1 + 2 + 3 = 6$$
some nmore text\par
some more text

\end{document}


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