Laurenso
With `article` document, by using `enumitem` package, I tried
```
\documentclass[12pt,a4paper]{article}
\usepackage{amsthm}
\usepackage{enumitem}
\begin{document}
\begin{enumerate}[label=\arabic*)]
\item First case
\begin{enumerate}[label=\alph*)]
\item $30^\circ$;
\item $45^\circ$;
\item $60^\circ$.
\end{enumerate}
\item Second case
\begin{enumerate}
\item $30^\circ$;
\item $45^\circ$;
\item $60^\circ$.
\end{enumerate}
\end{enumerate}
\end{document}
```
With `beamer`, I tried
```
\documentclass[13pt]{beamer}
\usetheme{CambridgeUS}
\begin{document}
\begin{enumerate}
\item First case
\begin{enumerate}
\item $30^\circ$;
\item $45^\circ$;
\item $60^\circ$.
\end{enumerate}
\item Second case
\begin{enumerate}
\item $30^\circ$;
\item $45^\circ$;
\item $60^\circ$.
\end{enumerate}
\end{enumerate}
\end{document}
```


with massage

Top Answer
samcarter
Beamer uses so-called "mini templates" to change the appearance of enumerate items. To use lower case letters, you can use the mini template `[a]`:
```
\documentclass{beamer}
\usetheme{CambridgeUS}
\usepackage{siunitx}
\begin{document}
\begin{frame}
\begin{enumerate}
\item First case:
\begin{enumerate}[a]
\item \ang{30};
\item \ang{45};
\item \ang{60}.
\end{enumerate}
\item second case:
\begin{enumerate}[a]
\item \ang{30};
\item \ang{45};
\item \ang{60}.
\end{enumerate}
\end{enumerate}
\end{frame}
\end{document}
```
