\documentclass[12pt]{article} % BB Mar 31 2011.
\usepackage{epsfig}
\textheight 9.0in \textwidth  6.0in \topmargin -0.4in \headsep 0.4in  
\oddsidemargin  0.25in  \evensidemargin 0.25in  

\def\sqr#1#2{{\vcenter{\hrule height.#2pt
   \hbox{\vrule width.#2pt height#1pt \kern#1pt
   \vrule width.#2pt} \hrule height.#2pt}}}
\def\square{{\mathchoice\sqr64\sqr64\sqr{4.2}3\sqr{3.0}3}}
\def\undertext#1{$\underline{\smash{\hbox{#1}}}$}
\pagestyle{empty}

\begin{document}

\begin{center}
{\bf ADVANCED DYNAMICS --- PHY 4241/5227}\\\vspace {2mm} 
{\bf SOLUTIONS -- SET 9}\\%
\end{center}
\setcounter{equation}{0}

\begin{description}

\item{(27)} 
$$ \triangle t = \frac{\tau}{\sqrt{1-(0.995)^2}} = 
   \frac{1051\times 10^{-15}\,s}{0.099875} = 1.0523\times 10^{-11}\,s$$
$$ \triangle x = \triangle t\times 0.995\,c = 0.00314\,m~~(c\ \rm speed\
   of\ light)\,.$$
\end{description}

% \begin{figure}[tb] \vspace{5pc}
% \centerline{\hbox{ \psfig{figure=figs/ladder.eps,width=7.5cm} }}
% \caption{Ladder for assignment~14.} \label{fig_lader} \end{figure}

\end{document}
