# Tikzmark; Tangent arrows

I am happy with this but I'd like to make the two drawn arrows tangent. Here is my minimal example:

\documentclass{article}
\usepackage{amsmath,tikz}
\usetikzlibrary{tikzmark}

\begin{document}
\begin{align*}
\textcolor{blue}{1\tikzmarknode{A}{}2}\bigg ( \dfrac{x\tikzmarknode{B}
{+}4}{4}-\dfrac{x\tikzmarknode{C}{-}3}{3} \bigg )&=\textcolor{blue}{12}\bigg
( \dfrac{11}{12} \bigg ) \\
\end{align*}
\begin{tikzpicture}[overlay,remember picture]
\draw[->,blue,thick,smooth,shorten >=1pt,shorten<=1pt,out=65,in=110,distance=.6cm] ([yshift=6pt]A.north) to ([yshift=2pt]B.north);
\draw[->,blue,thick,smooth,shorten >=1pt,shorten<=1pt,out=65,in=110,distance=.6cm] ([yshift=6pt]A.north) to ([yshift=2pt]C.north);
\end{tikzpicture}
\end{document}


This program gives:

BUT I am trying to get the two drawn lines tangent as in this image:

• Try out=90 for both and play with in until you like the result... second arrows in should be somehow greater than first... for example first in 110, second in 125 – koleygr Oct 17 '18 at 21:09
• You've not provided a MWE that we can compile. Also, at least for my version of tikzmark, there is no command \tikzmarknode. – A.Ellett Oct 17 '18 at 21:12
• Understood it is the newest version and not available on CTAN yet. My apologies. – MathScholar Oct 17 '18 at 21:27
• Technically, the lines are tangent. It's just that they don't stay tangent for long. Try using the looseness key on the longer arrow to get it to sweep out a bit more. – Andrew Stacey Oct 17 '18 at 21:35

I've taken a few liberties with your original posting. But here's a result. I elaborate below:

\documentclass[border=6pt]{standalone}

\usepackage{amsmath,tikz}
\usetikzlibrary{calc}

\newcommand\tikzmark[1]{\tikz[remember picture,overlay] \node[inner sep=0pt] (#1) {};}
\newcommand\tikzdouble[2]{\tikzmark{#11}#2\tikzmark{#12}}

\begin{document}

\begin{minipage}{5in}
\begin{align*}
\textcolor{blue}{\tikzdouble{A}{12}}
\bigg (
\dfrac{\tikzdouble{B}{x+4}}{4}
-\dfrac{\tikzdouble{C}{x-3}}{3}
\bigg )
&=
\textcolor{blue}{12}
\bigg (
\dfrac{11}{12}
\bigg )
\\
\end{align*}
\end{minipage}

\begin{tikzpicture}[overlay,remember picture,
my arrow style/.style={->,blue,thick,smooth,shorten >=1pt,shorten <=1pt}]
\foreach \myn in {A,B,C}
{
\coordinate (\myn) at ($(\myn1)!0.5!(\myn2)$);
}

\draw[my arrow style] ([yshift=8pt]A) .. controls ++(60:12pt) and ++(120:12pt) .. ([yshift=5pt]B);
\draw[my arrow style] ([yshift=8pt]A) .. controls ++(60:28pt) and ++(120:28pt) .. ([yshift=5pt]C);

\end{tikzpicture}
\end{document}


So, the first thing I've done is use the standalone class and because of that I have to put the align environment inside a minipage so it knows what the paper width is.

Next, I'm not sure what \tikzmarknode is supposed to actually do. I made my best guess and made my own command \tikzdouble. I'm also guessing that \tikzmarknode does some of the work I'm doing in the tikzpicture environment on its own.

I've also defined a style for the arrows to make the code a bit more readable.

The primary gist of what I've done is to use control points in lieu of the in= and out= keys for the directive to.

# Update

Here I've added a bit more muscle to \tikzdouble to do more of the grunt work for placing the nodes appropriately. But, it has been set up to operate in math mode.

The code

\documentclass[border=6pt]{standalone}

\usepackage{amsmath,tikz}
\usetikzlibrary{calc,fit}

%% this tikzdouble has been designed specifically for use in math mode
%% particular where it comes to measuring the height and depth of the text
%% being marked on either side with a node.
\newcommand\tikzdouble[2]{%%
\pgfmathsetmacro\aetmpA{depth("$#2$")}%%
\pgfmathsetmacro\aetmpB{height("$#2$")}%%
\tikz[remember picture,overlay] \node[inner sep=0pt] at (0,-\aetmpA pt)  (#1/tmp/1) {};%%
#2%%
\tikz[remember picture,overlay] \node[inner sep=0pt] at (0,\aetmpB pt) (#1/tmp/2) {};%%
\tikz[remember picture,overlay] \node[fit=(#1/tmp/1) (#1/tmp/2),inner sep=0pt] (#1) {};%%
}

\begin{document}

\begin{minipage}{5in}
\begin{align*}
\textcolor{blue}{\tikzdouble{A}{12}}
\bigg (
\dfrac{\tikzdouble{B}{x+4}}{4}
-\dfrac{\tikzdouble{C}{x-3}}{3}
\bigg )
&=
\textcolor{blue}{12}
\bigg (
\dfrac{11}{12}
\bigg )
\end{align*}
\end{minipage}

\begin{tikzpicture}[overlay,remember picture,
my arrow style/.style={->,blue,thick,smooth,shorten >=1pt,shorten <=1pt}]

\draw[my arrow style] (A.north) .. controls ++(60:12pt) and ++(120:12pt) .. (B.north);
\draw[my arrow style] (A.north) .. controls ++(60:32pt) and ++(120:24pt) .. (C.north);

\end{tikzpicture}
\end{document}

• The result is what I am looking for. I need some time to try and adapt it to my original posting. I forgot about the new version . It is discuss in this post: tex.stackexchange.com/questions/450135/… . I believe Loopspace created it. – MathScholar Oct 17 '18 at 21:57