I'm currently writing a document in which I have theorems both in the main chapters and in the appendices. The theorems in the main chapters are numbered 1.1, 1.2, 2.1 and so on, and the ones in the appendices are numbered A.1, A.2, B.1, etc.

I want to change the numbers of said enumerations to a "old style number" format. Currently I define my theorem style as

\newtheoremstyle{plane}{4pt}{6pt}{}{}{}{\newline}{.5em}{\thmname{#1}\thmnumber{\textbf{\oldstylenums{ #2}}} \thmnote{(#3)}}

and in the main chapters this works just fine, but in the appendices chapters the theorems change their numeration to .1, .2, etc. The letter of the appendix is no more!

What can I do? Due to format constraints, I cannot change the numbering of the appendices; their enumeration has to be with letters. I'm also working with the Garamondx font, which has the \oldstylenums command by default.

Thank you very much in advance. Here I provide a MWE:

\documentclass[letterpaper, 12pt, oneside]{book}
\usepackage[garamondx, cmbraces]{newtxmath}

\newtheoremstyle{plane}{4pt}{6pt}{}{}{}{\newline}{.5em}{\thmname{#1}\thmnumber{\textbf{\oldstylenums{ #2}}} \thmnote{(#3)}}



\chapter{Chapter Title}
\section{Section 1}


\chapter{Appendix 1}



1 Answer 1


Here is way to do it: change \newtheoremstyle[plane}{…} with

\newtheoremstyle{plane}{4pt}{6pt}{}{}{}{\newline}{.5em}{\fontfamily{zgmj}\selectfont\thmname{#1}\thmnumber{\textbf{ #2}}

enter image description here

However, in my opinion, it's not very nice: the chapter numbering should be changed to ‘small caps roman’ inside the theorem environment, and there should be not dot between chapter letter and theorem number, which is trickier to do.


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