7

Suppose the proof of a theorem contains a claim and its proof, and the proof of the claim completes the proof of the theorem. That is, no further text is required in the proof of the theorem after the end of the proof of the claim. For example:

\documentclass{article}
\usepackage{amsthm}
\newtheorem{theorem}{Theorem}
\newtheorem{claim}{Claim}
\begin{document}

\begin{theorem}
Today is Thursday.

\begin{proof}
We know that the day after Wednesday is always Thursday.
Thus the theorem follows from the following claim:

\begin{claim}
Yesterday was Wednesday.

\begin{proof}
My computer said so.
\end{proof}
\end{claim}
\end{proof}
\end{theorem}
\end{document}

By default the second QED symbol is placed a line below the first, even though there is no text on that line. It would seem more natural to place both QED symbols on the same line, next to each other, to indicate that the two (nested) proofs both conclude at that point. How can we achieve this? I've tried inserting the \qedhere command but it doesn't seem to help.

4

double the \qedsymbol.

in the preamble,

\let\oldqedbox\qedsymbol
\newcommand{\twoqedbox}{\oldqedbox\oldqedbox}

then, before the first \end{proof}, insert

\renewcommand{\qedsymbol}{\twoqedbox}

and before the second \end{proof}, insert

\renewcommand{\qedsymbol}{}

a "renewed" \qedsymbol will not persist.

amsthm was not designed to handle nested proofs; they are very rare.

  • But there's still the trailing QED box from the outer proof that shouldn't appear. I don't want an extra box, I want to move the box from the outer proof so that it appears together with the previous box. If you've doubled the box for the inside proof, we need to remove the one from the outer proof. – Ari Brodsky Dec 25 '14 at 19:55
  • Furthermore, I was hoping for an automatic solution - something we can change in the preamble so that this will happen automatically every time there are two (or more) nested end{proof}s with no text in between. – Ari Brodsky Dec 25 '14 at 19:57
2

You can fake the proof environment.

\begin{theorem}
Today is Thursday.
\end{theorem}  % moved to here

\begin{proof}
We know that the day after Wednesday is always Thursday.
Thus the theorem follows from the following claim:
\begin{claim}
Yesterday was Wednesday.
\end{claim}
\noindent\textit{\proofname.} My computer said so.\qedhere\qedsymbol
\end{proof}

enter image description here

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.