Circle two terms in an equation linking them by an arrow

Question

I'd like to know if it's possible to do something like that in an equation using beamer

Answer 1

It's easy to do with pstricks: just use the commands \circlenode and join them by an arc node connection, inside the psmatrix environment:

\documentclass[x11names]{article}
\usepackage[utf8]{inputenc}
\usepackage{pst-node}
\usepackage{auto-pst-pdf}

\begin{document}
\[
\begin{psmatrix}
\psset{linewidth=0.5pt, linecolor=Coral1,arrows=<->, arrowinset=0.15, arcangle=45, shortput=nab, labelsep=2pt}
 x = \circlenode{A}{a} + b + \circlenode{C}{c}
\ncarc[linewidth = 0.2pt, linecolor=black]{A}{C}^{\scriptstyle=}
\end{psmatrix}
\]
\end{document}

auto-pst-pdf must be loaded after pstricks, and pdflatex must be launched with the --enable-write18 switch (MiKTeX) or -shell-escape (TeX Live, MacTeX). To illustrate this, here is a screenshot of TeXmaker configuration:

Answer 2

This can be quite easily done using the tried and tested tikzmark idea, demonstrated throughout this site, for example How to draw arrows between circled coefficients of polynomials using tikz and How to draw arrows between parts of an equation to show the Math Distributive Property (Multiplication)?

Here's the output:

and the code:

% arara: pdflatex
% !arara: indent: {overwrite: yes}
\documentclass{beamer}
\usepackage{tikz}

% tikzmark command
\newcommand{\tikzmark}[2]{%
    \tikz[remember picture,baseline=(#1.base)]
    \node[circle,red,draw,text=black,anchor=center,inner sep=1pt] (#1) {#2};}
\begin{document}
\begin{frame}

    \[
        x =  \tikzmark{a}{a}+b+\tikzmark{c}{c}
    \]

    \tikz[overlay,remember picture]{\draw[blue,thick,->] (a.north) to [bend left=45] node[anchor=south]{$=$}(c.north);}
\end{frame}
\end{document}