Don't use such a long \text{...} command where it doesn't fit, perhaps?
It's hard to give a better answer than that without knowing what you
want to happen. The text comment on the first line obviously cannot fit there without wrapping. So one option would be to let it wrap by putting it in a parbox instead:
Code: Select all
\documentclass[12pt, a4paper, fleqn, leqno, twocolumn]{article}
\setlength{\columnseprule}{0.5pt}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage[lmargin=1cm, rmargin=1cm, tmargin=1cm, bmargin=1.2cm]{geometry}
\newcommand\thfore{\mathord{\therefore}\,}
\begin{document}
\begin{align*}
\thfore \angle LMK &=180^{\circ}-125^{\circ} \ \parbox[t]{4cm}{\raggedright (Cointerior angles bounded by parallel lines are equal)}\\
&=55^{\circ}
\end{align*}
\begin{align*}
u &= \arctan x & dv &= 1 \, dx
\\ du &= \frac{1}{1 + x^2} dx & v &= x.
\end{align*}
\end{document}
I guess the other option would be to move it, and e.g., use an \intertext command perhaps?
Code: Select all
\documentclass[12pt, a4paper, fleqn, leqno, twocolumn]{article}
\setlength{\columnseprule}{0.5pt}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage[lmargin=1cm, rmargin=1cm, tmargin=1cm, bmargin=1.2cm]{geometry}
\newcommand\thfore{\mathord{\therefore}\,}
\begin{document}
\begin{align*}
\thfore \angle LMK &=180^{\circ}-125^{\circ} \\ \intertext{(Cointerior angles bounded by parallel lines are equal)}
&=55^{\circ}
\end{align*}
\begin{align*}
u &= \arctan x & dv &= 1 \, dx
\\ du &= \frac{1}{1 + x^2} dx & v &= x.
\end{align*}
\end{document}
But what do you think should happen?
