Adding cross outs to math

Question

bayaraa surenjav asked to do something like

I came up with an answer before I realized it was closed.

@TejasShetty - Yeah, although technically they should close my question as well. — John Kormylo, Aug 01 '21 at 14:31
@TejasShetty - Generalize the question, or \tikzgroup? (See https://tex.stackexchange.com/questions/348566/how-to-create-special-math-macros-which-preserve-the-current-style) — John Kormylo, Aug 02 '21 at 03:22
generalise the answer so that it can work for any simple math calculation involving such cancelations — Tejas Shetty, Aug 02 '21 at 08:23
If all you want is cross outs, see https://tex.stackexchange.com/questions/246971/more-robust-strike-through-cross-out. In this case I was also using it to locate/add extra characters above and below. — John Kormylo, Aug 02 '21 at 13:12

score 3 · Accepted Answer · answered Aug 01 '21 at 14:28

Needless to say, this is not the only approach possible.

\documentclass{article}
\usepackage{amsmath}
\usepackage{tikz}
\usetikzlibrary{tikzmark}% not used yet
\newcommand{\tikzgroup}[2]% #1 = math, #2 = node name
  {\tikz[baseline=(#2.base), remember picture] {\node[inner sep=0pt] (#2) {$#1$};}}
\begin{document}
\hrule% size test
\begin{equation}
\rule[-2\baselineskip]{0pt}{5\baselineskip}% reserve space
\frac{\tikzgroup{4}{N1} \times \tikzgroup{5}{N2} \times \tikzgroup{3}{N3}}%
  {\tikzgroup{2}{D1} \times \tikzgroup{10}{D2}}
\end{equation}
\hrule% size test
\begin{tikzpicture}[overlay, remember picture]
  \draw[blue] (N1.north west) -- (N1.south east)% cross out
              (N2.north west) -- (N2.south east)
              (N3.north west) -- (N3.south east)
              (D1.north west) -- (D1.south east)
              (D2.north west) -- (D2.south east);
  \node[above={\dp\strutbox}, blue, inner sep=0pt] (NN1) at(N1.north) {2};
  \node[above={\dp\strutbox}, blue, inner sep=0pt] at (N2.north) {1};
  \node[below={\dp\strutbox}, blue, inner sep=0pt] at (D1.south) {1};
  \node[below={\dp\strutbox}, blue, inner sep=0pt] at (D2.south) (DD2) {2};
  \node[above={\dp\strutbox}, blue, inner sep=0pt] at(NN1.north) {1};
  \node[below={\dp\strutbox}, blue, inner sep=0pt] at (DD2.south) {1};
  \draw[blue] (NN1.north west) -- (NN1.south east)
              (DD2.north west) -- (DD2.south east);
\end{tikzpicture}
\end{document}

Adding cross outs to math

1 Answers1