deletions | additions       diff --git a/special rel.tex b/special rel.tex  index e42b1ce..21cac0d 100644  --- a/special rel.tex  +++ b/special rel.tex 
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\begin{equation}  \begin{split}  l' = \gamma l \frac{l}{\gamma}  \\ \end{split}  \end{equation}  where   \begin{equation}  \gamma = \sqrt{1-v^2} \frac{1}{\sqrt{1-v^2}}  \end{equation}  \subsection{Principle of Equivalence}