[Tex/LaTex] LaTeX – How to prevent extra whitespace when an equation falls at top of page

equationsspacing

I am a newbie to LaTeX, so if this question is simple to answer please forgive me.

I wish to keep the content in my document flush with the top margin. However, when an equation falls at the top of a page as in the MWE below, the equation environment skips down as if it were following a paragraph. How can I prevent this? Thank you in advance~

Added: I have already tried adding a \vspace{-xx} without success.

\documentclass[12pt]{report}
\usepackage[centertags]{amsmath}
\usepackage{lipsum}
\setlength{\topmargin}{-0.25in}
\begin{document}
%
\lipsum[1]
%
\cleardoublepage
%
\begin{equation}
\rho_{s} A r_{tt}(t,\ell) + \gamma I r_{t\ell\ell\ell\ell}(t,\ell) + E I r_{\ell\ell\ell\ell}(t,\ell) = f_{D}(t,\ell)
\end{equation}
%
\lipsum[2]
\end{document}

Best Answer

Typical math usage should form part of the textual content. So, just like one would use

... so let $x=y$ and then it is clear to see that ...

it is customary to use

... and therefore consider
\begin{equation}
  f(x) = ax^2 + bx + c.
\end{equation}
It follows that ...

Note that there is no paragraph break (or empty line) between the text and the display equation. This usage disallows displayed formulas to appear at the very top of the page.

In your instance, however, a forced \clearpage necessarily pushes the content immediately after the page break. This manual forcing is most likely countered by some manual intervention of the form:

%...
\clearpage
\mbox{}\par
\kern-2\baselineskip
\begin{equation}
  \rho_{s} A r_{tt}(t,\ell) 
    + \gamma I r_{t\ell\ell\ell\ell}(t,\ell) 
    + E I r_{\ell\ell\ell\ell}(t,\ell) = f_{D}(t,\ell)
\end{equation}
%...

The above holds for the default values of the document class. Changes to \abovedisplayshortskip or even \parskip should be incorporated in the vertical adjustment if they are modified.

Here's a minimal example showing the complete usage:

enter image description here

\documentclass[12pt]{report}
\usepackage[centertags]{amsmath}% http://ctan.org/pkg/amsmath
\usepackage{showframe,lipsum}% http://ctan.org/pkg/{showframe,lipsum}
\begin{document}
%
\lipsum[1]
%
\cleardoublepage
%
\setlength{\abovedisplayshortskip}{30pt}%
\mbox{}\par
\kern-2\baselineskip
\begin{equation}
\rho_{s} A r_{tt}(t,\ell) + \gamma I r_{t\ell\ell\ell\ell}(t,\ell) + E I r_{\ell\ell\ell\ell}(t,\ell) = f_{D}(t,\ell)
\end{equation}
%
\lipsum[2]
\end{document}

showframe was added to highlight the text block boundary.

More adjustments of this nature is available from the following sources:

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