8

I force to use two math environments in series, this will present a big space that I don't like, I saw this ansewer, he uses \\[-1ex] I don't want to use this method for each equation (I have a lot of equations), so is there any way to reduce the space between the two environments for the whole document?

Here is a simple example

\documentclass[a4paper,14pt]{extreport}
\usepackage{amsmath}
\begin{document}
\begin{align*}
     r &= \sqrt{x^2 + y^2} \\
     f &= m a \\
     A = \frac{\pi}{4} d^2
\end{align*}  
\begin{align*}
     \frac{\partial P}{\partial \theta} = \frac{P_{(i+1,j)} - P_{(i-1,j)}}{2 \Delta\theta}
\end{align*}
\end{document}

enter image description here

4
  • 5
    You should avoid using successive display math environments. Why not combine them into one?
    – Werner
    Aug 21, 2016 at 1:21
  • this example is simple and can be combined, but I have many cases that I forced to separate the equation in two or more environment, so I asked for a solution for such case. Aug 21, 2016 at 1:26
  • I can't imaging any case which force me to wrote series of successive equation which I can't merge it in one math environment (offered by amsmath/mathtools) . From reader side view math construct of number (different?) math environments is difficult to read and follow.
    – Zarko
    Aug 21, 2016 at 1:36
  • Never use align for a single equation: there's equation for that.
    – egreg
    Aug 21, 2016 at 7:40

3 Answers 3

9

Consecutive math displays should be avoided. If you really must group aligned display math and non-aligned content, use a single display math environment (here, gather*) and use an internal math environment to perform the alignment (here, aligned):

\documentclass[a4paper,14pt]{extreport}
\usepackage{amsmath}
\begin{document}
\begin{gather*}
\begin{aligned}
     r &= \sqrt{x^2 + y^2} \\
     f &= m a \\
     A &= \frac{\pi}{4} d^2
\end{aligned} \\
     \frac{\partial P}{\partial \theta} = \frac{P_{(i+1,j)} - P_{(i-1,j)}}{2 \Delta\theta}
\end{gather*}
\end{document}

enter image description here

1
5

You can nest align in gather (not the other way around). In the example code I use numbered equations but adding the * will produce the expected result.

\documentclass{article}
\usepackage{amsmath}

\begin{document}

The the basic solution consists in nesting \texttt{align} in \texttt{gather}
as shown below
\begin{gather}
  \begin{align}
  r &= \sqrt{x^2 + y^2} \\
  f &= m a \\
  A &= \frac{\pi}{4} d^2
  \end{align}\\
\frac{\partial P}{\partial \theta} = \frac{P_{(i+1,j)} - P_{(i-1,j)}}{2 \Delta\theta}
\end{gather}
Adding some phantoms also fixes the vertical spacing
\begin{gather}
  \begin{align}
  r &= \sqrt{x^2 + y^2}  \vphantom{\frac{1_{\mathstrut}}{2}}\\
  f &= m a               \vphantom{\frac{1_{\mathstrut}}{2}}\\
  A &= \frac{\pi}{4} d^2 \vphantom{\frac{1_{\mathstrut}}{2}}
  \end{align}\\
\frac{\partial P}{\partial \theta} = \frac{P_{(i+1,j)} - P_{(i-1,j)}}{2 \Delta\theta}
\end{gather}

\end{document}

enter image description here

If you have text between the two environments, just type it in, without blank lines in between.

\documentclass{article}
\usepackage{amsmath}

\begin{document}

If we have some word between the two environments, it's very easy:
\begin{align}
  r &= \sqrt{x^2 + y^2} \\
  f &= m a \\
  A &= \frac{\pi}{4} d^2
\end{align}  
where
\begin{equation}
\frac{\partial P}{\partial \theta} = \frac{P_{(i+1,j)} - P_{(i-1,j)}}{2 \Delta\theta}
\end{equation}
The important thing is not leaving blank lines before and after the math display
environments.

\end{document}

A blank line can follow a display, but only if a really new paragraph begins.

enter image description here

9
  • thanks for the answer, sometimes I need to write 'where' between the two environments, I want the word has no indent, how could I do that? Aug 21, 2016 at 15:47
  • @MuhammadAbdulrasool You need nothing special, I'll add the code.
    – egreg
    Aug 21, 2016 at 15:50
  • Thanks, but how can it be written inside the first environment (without indent) as in your first code? Aug 21, 2016 at 17:06
  • I tried this \text{where} \\ , but there is a lot of white space, I change the gather to align but still the same. Aug 21, 2016 at 17:44
  • @MuhammadAbdulrasool I don't understand what you are trying to do; the “where” word should go where I showed.
    – egreg
    Aug 21, 2016 at 18:01
1

I don't recommend it, but this gives you what you appear to want...

\documentclass[a4paper,14pt]{extreport}
\usepackage{amsmath}

\begin{document}
\setlength{\belowdisplayskip}{0pt}
\setlength{\abovedisplayskip}{0pt}
\setlength{\belowdisplayshortskip}{0pt}
\setlength{\abovedisplayshortskip}{0pt}
    \begin{align*}
        r &= \sqrt{x^2 + y^2} \\
        f &= m a \\
        A &= \frac{\pi}{4} d^2
    \end{align*}%  
\begin{align*}
        \frac{\partial P}{\partial \theta} = \frac{P_{(i+1,j)} - P_{(i-1,j)}}{2 \Delta\theta}
    \end{align*}
\end{document}
3
  • 1
    Won't this also remove the space before the first environment and after the last?
    – cfr
    Aug 21, 2016 at 1:40
  • (1) second math environment sesms to be gather*, (2) as mentioned @cfr, this changes is acceptable only locally, so you need to design a group in which your changes is valid. And I agree with you, that this is not recommended solution :-).
    – Zarko
    Aug 21, 2016 at 1:47
  • Yes, just group them.
    – JPi
    Aug 21, 2016 at 1:54

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