Footnote outside theorem environment

Question

I tried to add a footnote in a tcolorbox based theorem environment, which is showing right inside the theorem box. How to position footnote at the bottom of the page?

\documentclass[a4paper]{article}

% ------------------------------------------------------------------------------------------
%                                   Packages Required
% ------------------------------------------------------------------------------------------

\usepackage{amsthm}
\usepackage{tcolorbox}

% ------------------------------------------------------------------------------------------
%                           tcolorbox and theorem Environment
% ------------------------------------------------------------------------------------------

\tcbuselibrary{theorems}
\newtcbtheorem
  []% init options
  {theorem}% name
  {Theorem}% title
  {%
    colback=green!5,
    colframe=green!35!black,
    fonttitle=\bfseries,
  }% options
  {thm}% prefix

\makeatletter
% ------------------------------------------------------------------------------------------
%                                   User defined Commands
% ------------------------------------------------------------------------------------------

\newcommand{\reals}{\mathbb{R}}
\renewcommand{\qedsymbol}{$\blacksquare$}
\newcommand{\f}[1]{$f(#1)$}
\newcommand{\tcb@cnt@theoremautorefname}{Theorem}
\makeatother

% ------------------------------------------------------------------------------------------

\begin{document}

\begin{theorem}{Cauchy's Theorem}{}
Let C be a simple\footnote{A simple curve is one which does not cross itself.}. closed curve with continously turning tangents except possibly at a finite number of of points (otherwise curve must be smooth). If \f{z} is analytic on and inside C, then 
\begin{equation}
\oint_{C} f(z) \, dz = 0
\end{equation}
\end{theorem}

\end{document}

See Can I get a normal footnote in a minipage environment in LaTeX? How? Not an exact duplicate but the solution using \footnotemark/\footnotetext is the same. — campa, Dec 11 '19 at 12:45
Unrelated: \f{z} and $f(z)$ differ by one keystroke, and yet I believe the second one is much more clear. (Very personal opinion, of course.) — campa, Dec 11 '19 at 12:49
@campa Yes, but it prevents me from keep pressing dollar sign for inline formulas. In that case it's much quicker when you write math. — 147875, Dec 11 '19 at 12:54
It might be faster to type, but now your missing the clear separation between text and math in your code. So I agree with campa, not recommendable. — daleif, Dec 11 '19 at 17:39
Thank you @daleif, I'll make sure I won't repeat again. Is there any package or tips that would help me in faster typing the manuscript? — 147875, Dec 12 '19 at 09:53

Bernard · Accepted Answer · 2019-12-12T08:56:11.487

You can obtain what you want with etoolbox and the footnote package (from the mdwtools bundle):

\documentclass[a4paper]{article}

% ------------------------------------------------------------------------------------------
% Packages Required
% ------------------------------------------------------------------------------------------

\usepackage{amsthm}
\usepackage{tcolorbox}
% ------------------------------------------------------------------------------------------
% tcolorbox and theorem Environment
% ------------------------------------------------------------------------------------------

\tcbuselibrary{theorems}
\newtcbtheorem
  []% init options
  {theorem}% name
  {Theorem}% title
  {%
    colback=green!5,
    colframe=green!35!black,
    fonttitle=\bfseries,
  }% options
  {thm}% prefix

\makeatletter
% ------------------------------------------------------------------------------------------
% User defined Commands
% ------------------------------------------------------------------------------------------

\newcommand{\reals}{\mathbb{R}}
\renewcommand{\qedsymbol}{$\blacksquare$}
\newcommand{\f}[1]{$f(#1)$}
\newcommand{\tcb@cnt@theoremautorefname}{Theorem}
\makeatother

% ------------------------------------------------------------------------------------------

\usepackage{footnote}
\usepackage{etoolbox}
\BeforeBeginEnvironment{theorem}{\savenotes}
\AfterEndEnvironment{theorem}{\spewnotes}

\begin{document}

\vspace*{13cm}

\begin{theorem}{Cauchy's Theorem}{}
Let C be a simple\footnote{A simple curve is one which does not cross itself.}. closed curve with continously turning tangents except possibly at a finite number of of points (otherwise curve must be smooth). If \f{z} is analytic on and inside C, then
\begin{equation}
\oint_{C} f(z) \, dz = 0
\end{equation}
\end{theorem}

\end{document}

What is the purpose of using ∮ instead of \oint, Let C be instead of Let $C$ be , and inside C, instead of and inside $C$, and f(z) \, dz instead of f(z) \, \mathrm{d}z? — , Dec 11 '19 at 15:51
@Schrödinger'scat: For the first point, sorry, I didn't pay attention to what my editor was displaying. It is configured to do some ‘pretty display’, i.e. when it reads \oint, it displays ∮ (but saves the code as \oint). For the other points, I simply copied the code in the O.P., and didn't check whether this code corresponded to the image. — Bernard, Dec 11 '19 at 16:46
@Schrödinger'scat: What's is the difference between $dz$ and $\mathdrm{d}z$, since I don't find much difference between them. Please enlighten me, so that I can write better syntax. Any source for math-texing is fine. — 147875, Dec 12 '19 at 10:06
@Bernard your solution work great for short tcolorbox environments. But with breakable environments the footnote shows up after the box has been break. If the footnote call is at the beginning of the box, the footnote appears in the wrong page. Do you know how to fix this? — TeXtnik, Nov 20 '20 at 15:34

Footnote outside theorem environment

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