Your code more or less achieves what you want, doesn't it? There are some improvements that can be made, though:
- One should always put things in frames when working in the presentation mode of beamer.
- One can use
even odd rule
to avoid overpainting fills, in particular when you use a nontrivial fill opacity
.
- Set the
text opacity
to 1.
\textbf{...}
does not affect math expressions inside. You can use \boldsymbol
(or \boldmath
).
Result:
\documentclass[10pt, a4paper, serif, xcolor = {divpsnames, svgnames}]{beamer}
\usepackage{tikz}
\usepackage{amssymb}
\begin{document}
\begin{frame}[t]
\frametitle{A Venn diagram}
\begin{figure}
\centering
\begin{tikzpicture}
\begin{scope}[fill opacity = 0.5,text opacity=1]
\draw[fill = Green!70!white,even odd rule] (3.5, -2) rectangle (-3.5, 2)
node [below right=1ex] {$\boldsymbol{E}$}
(0, 0) circle[radius=1.7];
\draw[fill = white, draw = black,even odd rule] (0, 0) circle[radius=1.7]
(-.2, 0) circle[radius=1];
\draw[fill = Green!70!white, draw = black] (-.2, 0) circle[radius=1];
\node at (1.4, 0) (C) {$\boldsymbol{B}$};
\node at (.2, 0) (D) {$\boldsymbol{A}$};
\end{scope}
\end{tikzpicture}
\caption{Representa\c{c}\~ao da rela\c{c}\~ao $A \subset B$.}
\label{fig3}
\end{figure}
\end{frame}
\end{document}

Or with the E on the other side.
\documentclass[10pt, a4paper, serif, xcolor = {divpsnames, svgnames}]{beamer}
\usepackage{tikz}
\usepackage{amssymb}
\begin{document}
\begin{frame}[t]
\frametitle{A Venn diagram}
\begin{figure}
\centering
\begin{tikzpicture}
\begin{scope}[fill opacity = 0.5,text opacity=1]
\draw[fill = Green!70!white,even odd rule] (-3.5, -2) rectangle (3.5, 2)
node[below left=1ex] {$\boldsymbol{E}$} (0, 0) circle[radius=1.7];
\draw[fill = white, draw = black,even odd rule] (0, 0) circle[radius=1.7]
(-.2, 0) circle[radius=1];
\draw[fill = Green!70!white, draw = black] (-.2, 0) circle[radius=1];
\node at (1.4, 0) (C) {$\boldsymbol{B}$};
\node at (.2, 0) (D) {$\boldsymbol{A}$};
\end{scope}
\end{tikzpicture}
\caption{Representa\c{c}\~ao da rela\c{c}\~ao $A \subset B$.}
\label{fig3}
\end{figure}
\end{frame}
\end{document}
