# Add an equation at the bottom of a two-column article

How can I place a two-column equation (a large equation that does not fit in one column) at the bottom of a page?

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groups.google.com/group/latexusersgroup/browse_thread/thread/… describes an approach using multicols. – N.N. Sep 12 '11 at 12:21
If you are trying to do that in an IEEE Journal paper (notoriously 2-column), then you may want to read the style guide, where they give another approach, using \begin{figure*} (which has some limitations, though... they recommend to break the equation across multiple lines instead). The details can be found in the IEEE Author Digital Tool Box, section X-D1. – Count Zero Sep 12 '11 at 13:29

You can use the multicol package. Either you end a multicol environment before the equation and restart it after, or you define an environment like this:

\documentclass[parskip]{scrartcl}
\usepackage[margin=15mm]{geometry}
\usepackage{multicol}
\usepackage{lipsum}
\pagestyle{empty}

\newcommand{\OneColEqu}[1]{%
\end{multicols}%
$$% #1$$%
\begin{multicols}{2}%
}

\begin{document}
\begin{multicols}{2}
\lipsum[1]
\end{multicols}
$$\int\limits_{x=0}^{x=5}(x^2+2x-3) dx = \left[ \frac{1}{3}x^3+x^2-3x+C \right]^{x=5}_{x=0} = \frac{125}{3}+25-15+C-C= \frac{155}{3}$$
\begin{multicols}{2}
\lipsum[2]
\OneColEqu{\int\limits_{x=0}^{x=5}(x^2+2x-3) dx = \left[ \frac{1}{3}x^3+x^2-3x+C \right]^{x=5}_{x=0} = \frac{125}{3}+25-15+C-C= \frac{155}{3}}
\lipsum[3]
\end{multicols}

\end{document}


Both approches yield the same, but the own command probably is more convineant:

Edit 1: Putting the equation always on the bottom can be achieved by defining a custom float with the float package:

\documentclass[parskip]{scrartcl}
\usepackage[margin=15mm]{geometry}
\usepackage{multicol}
\usepackage{float}
\usepackage{lipsum}
\pagestyle{empty}

\floatstyle{plain}
\newfloat{twocolequfloat}{b}{zzz}
\floatname{twocolequfloat}{Equation}

\newcommand{\OneColEqu}[1]{%
\end{multicols}%
\begin{twocolequfloat}%
\ensuremath{\hfill #1 \hfill}%
\end{twocolequfloat}%
\begin{multicols}{2}%
}

\begin{document}
\begin{multicols}{2}
\lipsum[1-3]
\OneColEqu{\int\limits_{x=0}^{x=5}(x^2+2x-3) dx = \left[ \frac{1}{3}x^3+x^2-3x+C \right]^{x=5}_{x=0} = \frac{125}{3}+25-15+C-C= \frac{155}{3}}
\lipsum[3-7]
\OneColEqu{\int\limits_{x=0}^{x=5}(x^2+2x-3) dx = \left[ \frac{1}{3}x^3+x^2-3x+C \right]^{x=5}_{x=0} = \frac{125}{3}+25-15+C-C= \frac{155}{3}}
\lipsum[8-14]
\OneColEqu{\int\limits_{x=0}^{x=5}(x^2+2x-3) dx = \left[ \frac{1}{3}x^3+x^2-3x+C \right]^{x=5}_{x=0} = \frac{125}{3}+25-15+C-C= \frac{155}{3}}
\lipsum[15]
\end{multicols}
\end{document}

• \floatstyle{plain} same stlye as LaTex (no rules around the float)
• \newfloat{twocolequfloat}{b}{zzz} new float twocolequfloat, which is always aligned bottom, for posiible use in listof... or something the file .zzz will be written
• \floatname{twocolequfloat}{Equation} name displaed e.g. if you use labels

Then we use this environment for our math:

• \begin{twocolequfloat}% begin environment
• \ensuremath{\hfill #1 \hfill}% make sure formula set in mathmode, use \hfill to center it
• \end{twocolequfloat}% end environment

However, the formula will always be set to the bottom of the page. If your text ends after 20% of the page, the formula will be far away.

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Thanks Tom. But I want it at the bottom of page not in the middle of it – amir Sep 13 '11 at 20:22
So you wnat to write text (say two pages), somewhere write a formula, which is automatically moved to the bottom of the nearest apge? – Tom Bombadil Sep 13 '11 at 20:30
Yes. I want that – amir Sep 13 '11 at 20:39
There you go, almost perfect. If you know how to check if the last page is completely filled and conditionally alter the environment... – Tom Bombadil Sep 14 '11 at 0:26