7

For example, this is what I am looking for:

enter image description here

Usually for limits where the value is 0 or 1 of a particular expression (e^x) in this case, you might see something like a tilted 45 degrees equal sign, and the value of that expression.

Not sure how to do it here.

Maybe something like a overbrace without the actual overbrace visible?

5
  • 1
    Why not this?
    – Werner
    Nov 23 '18 at 22:24
  • 5
    e^x is not equal to 1.
    – egreg
    Nov 23 '18 at 22:32
  • 1
    @marmot I find it wrong: it is not an equality and will confuse the students, rather than help them.
    – egreg
    Nov 23 '18 at 22:35
  • @marmot: Sure, there are conditions imposed on A and B - they both need to have their own respective limits, but that is besides the point here. Do you find the product of the limits is the limit of the products confusing? I find the =1 coloured, slanted superscript confusing.
    – Werner
    Nov 23 '18 at 22:36
  • 2
    Please ignore whether the math is correct or not correct. This is simply what I have seen around in class, where if we are evaluating the limit at x=0, then clearly e^0 = 1, this is why I have the = 1
    – K Split X
    Nov 24 '18 at 1:09
12

If you only want to draw one of those, this might be a bit of an overkill, but if you plan to do several annotations of that kind and wish to have access to more fancy features, this might be a reasonable way to go.

\documentclass{article}
\usepackage{amsmath}
\usepackage{tikz}
\usetikzlibrary{tikzmark}
\begin{document}
\[\lim_{x\to0}\tikzmarknode{ex}{\mathrm{e}^x}\left(2+4x\right)~=~2\]
\begin{tikzpicture}[overlay,remember picture]
\path[red] ([xshift=1pt,yshift=1pt]ex.north east) -- ++(45:{width("=")*1pt-1pt})
node[midway,sloped]{$=$} node[above right=-2pt]{$1$};
\end{tikzpicture}
\end{document}

enter image description here

Arguably somewhat clearer alternatives include

\documentclass{article}
\usepackage{mathtools}
\usepackage{tikz}
\usetikzlibrary{tikzmark}
\begin{document}
\[\lim_{x\to0}\tikzmarknode{ex}{\mathrm{e}^x}\left(2+4x\right)~=~2\]
\begin{tikzpicture}[overlay,remember picture]
\draw[red,->] ([xshift=1pt,yshift=1pt]ex.north east) --
++(45:{width("$\scriptstyle x\to0$")*1pt})
node[midway,sloped,above]{$\scriptstyle x\to0$} node[above right=-1pt]{$1$};
\end{tikzpicture}
\end{document}

enter image description here

which illustrates what I mean by "more fancy options".

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