How do I put \begin{align} in tcbox?

Question

I want to cross out sentences and equations. I used the solution given in Cross out words with overlapping to nearby words

\documentclass{article}\usepackage{xcolor} \usepackage[most]{tcolorbox}

\tikzset{crossout/.style={thick,red,shorten >=-.5cm,shorten <=-.5cm}}

\begin{document}

\tcbox[tcbox raise base,
breakable,nobeforeafter, enhanced jigsaw, opacityback=0, sharp corners, parbox=false, boxrule=0pt, top=0pt,bottom=0pt,left=0pt,right=0pt, boxsep=0pt, frame hidden, parbox=false, 
  finish={\draw[crossout] (frame.south west)--(frame.north east);\draw[crossout] (frame.south east)--(frame.north west);}]{

  Therefore we have

  \begin{align*}
(t=1, m=[0], s=(2,2)) \otimes (t=1, m=[0], s=(4,4)) &= (1, [0,2], (4,4)) \\
(t=3, m=[0], s=(4,4)) \otimes (t=3, m=[0], s=(5,5)) &= (3, [0,4], (5,5)) \\
\end{align*}

}

\end{document}

But it throws exception:

Missing \endgroup inserted.

<inserted text> 
                \endgroup 
l.18 }

I've inserted something that you may have forgotten.
(See the <inserted text> above.)
With luck, this will get me unwedged. But if you
really didn't forget anything, try typing `2' now; then
my insertion and my current dilemma will both disappear.

 name.tex, line 18
Missing } inserted.

<inserted text> 
                }
l.18 }

I've inserted something that you may have forgotten.
(See the <inserted text> above.)
With luck, this will get me unwedged. But if you
really didn't forget anything, try typing `2' now; then
my insertion and my current dilemma will both disappear.

 name.tex, line 18
LaTeX Error: \begin{document} ended by \end{align*}.

See the LaTeX manual or LaTeX Companion for explanation.
Type  H <return>  for immediate help.
 ...                                              

l.18 }

Your command was ignored.
Type  I <command> <return>  to replace it with another command,
or  <return>  to continue without it.

Answer 1

Why not using tcolorbox?

\documentclass{article}
\usepackage{xcolor}
\usepackage[most]{tcolorbox}

\tikzset{crossout/.style={thick,red,shorten >=-.5cm,shorten <=-.5cm}}

\begin{document}

\begin{tcolorbox}[
  breakable,
  nobeforeafter,
  enhanced jigsaw,
  opacityback=0,
  sharp corners,
  parbox=false,
  boxrule=0pt,
  top=0pt,
  bottom=0pt,
  left=0pt,
  right=0pt,
  boxsep=0pt,
  frame hidden,
  finish={
    \draw[crossout] (frame.south west)--(frame.north east);
    \draw[crossout] (frame.south east)--(frame.north west);
  }
]
Therefore we have
\begin{align*}
(t=1, m=[0], s=(2,2)) \otimes (t=1, m=[0], s=(4,4)) &= (1, [0,2], (4,4)) \\
(t=3, m=[0], s=(4,4)) \otimes (t=3, m=[0], s=(5,5)) &= (3, [0,4], (5,5))
\end{align*}
Be careful not to do this.
\end{tcolorbox}

\end{document}

Answer 2

It is not so easy to put align into boxes (you essentially have to use a minipage), so tcolorbox has a key for the AMS environments. In your case, one can use ams align* lower. Of course, one needs to remove the separator with lower separated=false. I also switched to \begin{tcolorbox}...\end{tcolorbox} instead of \tcbox{...}.

\documentclass{article}
\usepackage{amsmath} 
\usepackage[most]{tcolorbox}

\tikzset{crossout/.style={thick,red,shorten >=-.5cm,shorten <=-.5cm}}

\begin{document}

\begin{tcolorbox}[tcbox raise base,
breakable,ams align* lower,lower separated=false,
nobeforeafter, enhanced jigsaw, opacityback=0, sharp corners, 
parbox=false,
boxrule=0pt, top=0pt,bottom=0pt,left=0pt,right=0pt, boxsep=0pt, frame hidden,
  finish={\draw[crossout] (frame.south west)--(frame.north east);
  \draw[crossout] (frame.south east)--(frame.north west);}]
  Therefore we have
\tcblower
(t=1, m=[0], s=(2,2)) \otimes (t=1, m=[0], s=(4,4)) &= (1, [0,2], (4,4)) \\
(t=3, m=[0], s=(4,4)) \otimes (t=3, m=[0], s=(5,5)) &= (3, [0,4], (5,5)) \\
\end{tcolorbox}
\end{document}

Answer 3

Obtaining what you want with pstricks is easy:

\documentclass{article}
\usepackage{amsmath}
\usepackage[most]{tcolorbox}
\usepackage{pst-node, auto-pst-pdf}

\begin{document}

\psDefBoxNodes{E}{\centering%
$ \begin{aligned}
 (t=1, m=[0], s=(2,2)) \otimes (t=1, m=[0], s=(4,4)) &= (1, [0,2], (4,4)) \\
(t=3, m=[0], s=(4,4)) \otimes (t=3, m=[0], s=(5,5)) &= (3, [0,4], (5,5))
\end{aligned} $%
}%
\psset{linecolor=red, nodesep=1.5em}
\ncline{E:tl}{E:br}
\ncline{E:bl}{E:tr}

\end{document}