[Tex/LaTex] How to align text to the right in math mode

horizontal alignmentmath-mode

I have a table of formulas, some have a description next to them, I want the equations to appear left flush and the text between parentheses right flush. I was writing it in the following way.

\documentclass[letterpaper,10 pt,twocolumn,fleqn]{article}
\setlength{\columnsep}{2.5cm}
\usepackage[inner=2.5cm,outer=2.5cm,bottom=2.5cm,top=2.5cm,landscape]{geometry}
\usepackage{nopageno,array,graphicx,amsbsy,amsfonts} 
\usepackage{amsmath} 
\begin{document}       
\[{\bf P} = \int_{t_i}^{t_f}{\bf F}\,dt = \Delta{\bf p}\mbox{\hspace{7mm} (Impulse) }\]
\[\frac{dA}{dt} = \frac{l}{2\mu}=cte \mbox{\hspace{7mm} (Kepler's Second Law) }\]
\end{document}

but the alignment is different for each equation.

Best Answer

You can use \tag* from the amsmath package.

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\[
\mathbf{P} = \int_{t_i}^{t_f}\mathbf{F}\,dt = \Delta \mathbf{p}\tag*{(Impulse) }
\]
\[
\frac{dA}{dt} = \frac{l}{2\mu}=cte \tag*{(Kepler's Second Law) }
\]
\end{document}

Note that \mathbf is preferable to \bf; see this question for more details.

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