Equation and Formula
\vec{r}
\dot{r}
\ddot{r}
\dddot{r}
$ $
\[ \]
\begin{equation}
\end{equation}
\begin{widetext}
\end{widetext}
\begin{equation}
\begin{split}
x &= a + b\\
&= c + d\\
&= y
\end{split}
\end{equation}
\begin{equation}
y =
\left\{
\begin{array}{ccc}
1 & , & x > 0\\
-1 & , & x = 0\\
0 & , & x < 0\\
\end{array}
\right.
\end{equation}
\verb "main.c"
{\small
\begin{verbatim}
\end{verbatim}
}
\usepackage{etoolbox}
\BeforeBeginEnvironment{verbatim}{\def\baselinestretch{1}} % make verbatim single spaced
