% just an example of the useage of cursor.sty

\documentclass{article}
\usepackage{example,cursor}
\begin{document}



\begin{example}
\cursorformula{D^\sigma_{\!x|a}
\LRc{f(x) =}{\frac{d^\sigma}{dx^\sigma}}
f(x) = \int_a^x f(x) (dx)^{-\sigma}}
$$D^\sigma_{\!x|a}
\LRc{f(x) =}{\frac{d^\sigma}{dx^\sigma}}
f(x) = \int_a^x f(x) (dx)^{-\sigma}$$
$D^\sigma_{\!x|a}
\LRc{f(x) =}{\frac{d^\sigma}{dx^\sigma}}
f(x) = \int_a^x f(x) (dx)^{-\sigma}$
\end{example}

\begin{example}
\cursorformula{D^\sigma_{\!x|a} f(x) =
\LRc{}{\frac{d^\sigma}{dx^\sigma}}
f(x) = \int_a^x f(x) (dx)^{-\sigma}}
$${D^\sigma_{\!x|a} f(x) =
\LRc{}{\frac{d^\sigma}{dx^\sigma}}
f(x) = \int_a^x f(x) (dx)^{-\sigma}}$$
\end{example}

\begin{example}
\cursorformula{D^\sigma_{\!x|a}
\Rc{f(x) = }{} \frac{d^\sigma}{dx^\sigma}
f(x) = \int_a^x f(x) (dx)^{-\sigma}}
$${D^\sigma_{\!x|a}
\Rc{f(x) =}{}\frac{d^\sigma}{dx^\sigma}
f(x) = \int_a^x f(x) (dx)^{-\sigma}}$$
\end{example}


\begin{example}
\cursorformula{ D^\sigma_{\!x|a}
f(x)=\frac{d^\sigma}{\Rc{dx^\sigma}}
f(x) = \int_a^x f(x) (dx)^{-\sigma}
}
$${ D^\sigma_{\!x|a}
f(x)=\frac{d^\sigma}{\Rc{dx^\sigma}}
f(x) = \int_a^x f(x) (dx)^{-\sigma}
}$$
\end{example}

\begin{example}
$${ D^\sigma_{\!x|a}
f(x)=\frac{d^\sigma}{\LRc{}{dx^\sigma}}
f(x) = \int_a^x f(x) (dx)^{-\sigma}
} $$
\end{example}



\end{document}