Vjylku

I'm using the package amsthm and I like to define my own proof environment, where the title proof is replaced by Beweis.

So far, I tried

newenvironment{bew}{begin{proof}[textsc{textbf{Beweis:}}]}{end{proof}}

and this works fine. But now I like to improve the environment so that the argument should stay between Beweis and :

For example

 begin{bew}[von Theorem 2.1]

     Nice proof.

 end{bew}

should look like

Beweis von Theorem 2.1: Nice proof.

What you need is just changing the period with a colon. Unfortunately, amsmath hardwires the period, so we need to patch proof in order to remove the dependency.

The name will switch to “Beweis” as soon as you load babel with an option for German, usually ngerman if you adhere to the “neue Rechtschreibung”.

documentclass{article}

usepackage[T1]{fontenc}

usepackage[ngerman]{babel}



usepackage{amsthm}

usepackage{xpatch}



% we need to substitute . with a generic command

xpatchcmd{proof}{.}{proofpunctuation}{}{}



newcommand{proofpunctuation}{:} % change to your liking



begin{document}



begin{proof}

Das ist ein schöner Beweis.

end{proof}



end{document}

The input

begin{proof}[Beweis von Satz 1]

Das ist ein schöner Beweis.

end{proof}

will produce the expected result.

If you prefer boldface, another patch is in order.

documentclass{article}

usepackage[T1]{fontenc}

usepackage[ngerman]{babel}



usepackage{amsthm}

usepackage{xpatch}



% we need to substitute . with a generic command

xpatchcmd{proof}{.}{proofpunctuation}{}{}

xpatchcmd{proof}{itshape}{prooffont}{}{}



newcommand{proofpunctuation}{:}

newcommand{prooffont}{bfseries}



begin{document}



begin{proof}

Das ist ein schöner Beweis.

end{proof}



begin{proof}[Beweis von Satz 1]

Das ist ein schöner Beweis.

end{proof}



end{document}

If your font supports boldface small caps (few fonts do), you can say

newcommand{prooffont}{scshapebfseries}

A syntax such as begin{proof}[von Satz 1] to automatically supply “Beweis” could be done too, but I'd not do it.

documentclass{article}

usepackage[T1]{fontenc}

usepackage[ngerman]{babel}



usepackage{amsthm}

usepackage{xpatch}



% we need to substitute . with a generic command

xpatchcmd{proof}{.}{proofpunctuation}{}{}

xpatchcmd{proof}{itshape}{prooffont}{}{}

xpatchcmd{proof}{#1}{proofnameifxproofname#1else #1fi}{}{}



newcommand{proofpunctuation}{:}

newcommand{prooffont}{bfseries}



begin{document}



begin{proof}

Das ist ein schöner Beweis.

end{proof}



begin{proof}[von Satz 1]

Das ist ein schöner Beweis.

end{proof}



end{document}

You can also do with a new environment, which avoids patching.

documentclass{article}

usepackage[T1]{fontenc}

usepackage[ngerman]{babel}



usepackage{amsthm}

usepackage{xparse}



NewDocumentEnvironment{bew}{o}

 {proof[normalfontbfseriesproofnameIfValueT{#1}{ #1}:]}

 {endproof}



begin{document}



begin{bew}

Das ist ein schöner Beweis.

end{bew}



begin{bew}[von Satz 1]

Das ist ein schöner Beweis.

end{bew}



end{document}