multicol package causes underfull \hbox

Question

I would like to have two (or three) equations in the same line, side-by-side. I tried to do it with the multicol package:

\documentclass[a4paper]{article}
\usepackage{multicol}
\begin{document}   

\begin{multicols}{2}
  \begin{equation*}
    K_P=\frac{0.9}{\mathcal{R} t_d}=0.40
  \end{equation*} % here I get the 'underfull' warning
  \break
  \begin{equation*}
    t_I=\frac{t_d}{0.3}=57.3
  \end{equation*}
\end{multicols}

\end{document}

The output is

P.S. Also, I noticed a large vertical space between the text and the equations. Can I reduce it?

It is possible to use multicol, but it is much easier to use a table. Do you have specific reasons for using multicol? — Sveinung, May 16 '19 at 18:20
No, I used it because when I googled "equations side by side latex" I got this question: https://tex.stackexchange.com/questions/32701/side-by-side-equations-with-equation-numbers-for-each — Lorenzo B., May 16 '19 at 18:23

score 8 · Accepted Answer · answered May 16 '19 at 19:16

Why not simply use the align* or flalign* environments?

\documentclass[a4paper]{article}
\usepackage[showframe]{geometry}
\usepackage{amsmath}
\usepackage{lipsum} 

\begin{document}

\lipsum[10]
\begin{align*}
      K_P & =\frac{0.9}{\mathcal{R} t_d}=0.40
 &
    t_I & =\frac{t_d}{0.3}=57.3 &K_P t_I & =3\mathcal{R}
\end{align*}
\lipsum[11]
\begin{flalign*}
      K_P & =\frac{0.9}{\mathcal{R} t_d}=0.40
 &
    t_I & =\frac{t_d}{0.3}=57.3 &K_P t_I & =3\mathcal{R}
\end{flalign*}
\lipsum[12]

\end{document}

score 3 · Answer 2 · answered May 16 '19 at 17:52

You could use tabularx:

\documentclass[a4paper]{article}
\usepackage{multicol}
\usepackage{amsmath}
\usepackage{lipsum}
\usepackage{tabularx}
\begin{document}   
\lipsum[4]

\noindent
\begin{tabularx}{\textwidth}{XX}
  \begin{equation*}
    K_P=\frac{0.9}{\mathcal{R} t_d}=0.40
  \end{equation*} % here I get the 'underfull' warning
  &
  \begin{equation*}
    t_I=\frac{t_d}{0.3}=57.3
  \end{equation*}
\end{tabularx}

\lipsum[4]

\end{document}

multicol package causes underfull \hbox

2 Answers2