fix issue gaoxiang12#35

chapters/rigidBody.tex

@@ -827,7 +827,7 @@ \subsection{Data Structure of the \textit{Eigen} Geometry Module}
 }
 \end{lstlisting}
 
-The various forms of expression in \textit{Eigen} are summarized below. Note that each type has both single and double data types and, as before, cannot be automatically converted by the compiler. Taking the double-precision as an example, you can simply change the last ``d'' to ``f'' to use a single-precision data structure.
+The various forms of expression in \textit{Eigen} are summarized below. Note that each type has both single and double precision types and, as before, cannot be automatically converted by the compiler. Taking the double-precision as an example, you can simply change the last ``d'' to ``f'' to use a single-precision data structure.
 \begin{itemize}
 	\item Rotation matrix ( $ 3  \times  3 $ ): Eigen::Matrix3d.
 	\item Rotation vector ( $ 3  \times  1 $ ): Eigen::AngleAxisd.