15

Here's what my equation looks like; it's in an align* environment:

equation

I want to put a circle around $\varepsilon \frac{dL}{d\varepsilon}$ and everything else unchanged.

Q: How do I draw a circle around a term in an align* equation?

I found that \textcircled doesn't work in math mode and \tikz \node[circle,draw] { $\varepsilon \frac{dL}{d\varepsilon}$}; is not suitable as it shifts the term:

enter image description here

I get fairly close using \boxed{\varepsilon \frac{dL}{d\varepsilon}}, but it's not a circle:

enter image description here

Here's a working example:

\documentclass{article}

\usepackage{amsmath,amssymb}

\begin{document}

\begin{align*}
L(q+\varepsilon) = L(q) + \varepsilon \frac{dL}{d\varepsilon} + \cdots \\
\end{align*}

\end{document}

1 Answer 1

22

The TikZ-way you tried works, you just forgot to set the baseline of the tikzpicture to the baseline of the text inside the math node. Here is an adjusted solution which also respects the mathstyle outside of the node.

\documentclass{article}
\usepackage{mathtools}% superior to amsmath
\usepackage{tikz}
\makeatletter
\newcommand\mathcircled[1]{%
  \mathpalette\@mathcircled{#1}%
}
\newcommand\@mathcircled[2]{%
  \tikz[baseline=(math.base)] \node[draw,circle,inner sep=1pt] (math) {$\m@th#1#2$};%
}
\makeatother
\begin{document}

\begin{align*}
  L(q+\varepsilon)
  &= L(q) + \mathcircled{\varepsilon \frac{dL}{d\varepsilon}} + \cdots \\
  &= \textstyle L(q) + \mathcircled{\varepsilon \frac{dL}{d\varepsilon}} + \cdots \\
  &= \scriptstyle L(q) + \mathcircled{\varepsilon \frac{dL}{d\varepsilon}} + \cdots \\
  &= \scriptscriptstyle L(q) + \mathcircled{\varepsilon \frac{dL}{d\varepsilon}} + \cdots
\end{align*}

\end{document}

enter image description here

7
  • Excellent. Thanks, that's exactly what I'm after. Commented Jun 11, 2015 at 6:22
  • 1
    What is the meaning of $\m@th#1#2$. Would you please explain the code.
    – Fadwa
    Commented Nov 18, 2015 at 19:28
  • 2
    @Misaki The definition is \m@th: macro:->\mathsurround \z@. That is to say, it sets \mathsurround to 0pt. Commented Nov 18, 2015 at 20:00
  • I am trying to add two circles instead of one, i used your code and add one in another \mathcircled{\mathcircled{\varepsilon \frac{dL}{d\varepsilon}}}, but the spacing between them is large besides i can't change the color of the other. would you please help. Thanks
    – Fadwa
    Commented Nov 19, 2015 at 5:21
  • @Misaki Instead of nesting, use this definition of \dblmathcircled: \newcommand\dblmathcircled[1]{\mathpalette\@dblmathcircled{#1}} \newcommand\@dblmathcircled[2]{\tikz[baseline=(math.base)]\node[draw,circle,double,inner sep=1pt] (math) {$\m@th#1#2$};}. Commented Nov 19, 2015 at 9:25

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .