Equation numbering using floating tcolorbox

Question

There is an issue in the numbering of equation when using a floating tcolorbox. I would like the equations to be numbered in the order of appearance.

Here is a MWE

\documentclass{article}
\usepackage{tikz}
\usepackage{tcolorbox}
\newtcolorbox{myframe}[1][]{#1}
\begin{document}
\begin{equation} 1+2=3 \end{equation}
used with theorem \ref{theorem}
\begin{myframe}[float,floatplacement=t]
This is the theorem:
\begin{equation} 1+1=2. \label{theorem} \end{equation}
\end{myframe}
gives
\begin{equation} 2+2=4. \end{equation}
\end{document}

Is there a way to number the equations correctly ? Thanks.

EDIT To be more precise, I want the numbering to be in the order of appearance, wherever the float is positioned.

Answer 1

This uses the \tag command from amsmath. For this to work, you will need to add \mytag to every numbered equation. It will take two runs to relabel the equations, and 3 runs to get \ref right.

If you want the chapter number prefixed to the equation number, you will have to reformat the \tag inside \mytag.

\documentclass{article}
\usepackage{amsmath}
\usepackage{tikz}
\usepackage{tcolorbox}
\newtcolorbox{myframe}[1][]{#1}

\newcounter{myequation}

\newcommand{\neweqmap}[1]% #1 = original euqation number
  {\stepcounter{myequation}%
  \expandafter\xdef\csname eqmap#1\endcsname{\themyequation}}

\makeatletter
\newcommand{\mytag}{\@ifundefined{eqmap\theequation}{}%
  {\stepcounter{equation}%
    \tag{\csname eqmap\theequation\endcsname}}%
  \protected@write\@auxout{}{\string\neweqmap{\theequation}}}
\makeatother

\begin{document}
\begin{equation} 1+2=3 \mytag \end{equation}
used with theorem \ref{theorem}
\begin{myframe}[float,floatplacement=t]
This is the theorem:
\begin{equation} 1+1=2. \mytag\label{theorem} \end{equation}
\end{myframe}
gives
\begin{equation} 2+2=4. \mytag \end{equation}
\end{document}

Answer 2

Just change the order of appearance:

\documentclass{article}
\usepackage{tikz}
\usepackage{tcolorbox}
\newtcolorbox{myframe}[1][]{#1}
\begin{document}
\begin{myframe}[float,floatplacement=t]
This is the theorem:
\begin{equation} 1+1=2. \label{theorem} \end{equation}
\end{myframe}
\begin{equation} 1+2=3 \end{equation}
used with theorem \ref{theorem}
gives
\begin{equation} 2+2=4. \end{equation}
\end{document}