# How to switch from serif to sans-serif in title of tcb-theorems?

I have written a document, that uses tcb-theorems to enclose theorems in the text. I would like to try out how my document looks if the titles were written in the sans serif version of the font I am using. So my question is: How can I change the style of the titles (and maybe the text) of the tcbtheorem environment that I have written below from serif to sans-serif?

\documentclass[a4paper, 11pt]{book}

\usepackage[a4paper,left=3cm,right=3cm,top=3cm,bottom=3cm]{geometry}

\usepackage{lmodern}
\usepackage{tcolorbox}
\tcbuselibrary{theorems}

\newtcbtheorem[number within=section]{theorem}{Theorem}
{colback=blue!25,colframe=blue!25!black,fonttitle=\bfseries}{th}

\begin{document}

afasdsf

\begin{theorem}{Some Titel}{}
Some Text.
\end{theorem}

\end{document}

• fonttitle=\bfseries\sffamily ? – user194703 Jun 11 at 18:09
• @Schrödinger'scat Might want to throw in a \boldmath if they’ll be using math mode within the title. If you want bold sans-serif math, scroll down and read some of the answers further down this page. – Davislor Jun 11 at 19:13
• @Davislor I agree. Of course, if our interpretation of the question is correct. BTW, there seems to be a disagreement between users whether or not math should be made bold in e.g. a section, when the surrounding text is bold. I definitely think one should, some disagree. – user194703 Jun 11 at 19:17
• @Davislor I do not know how to find the thread, but I remember to have had this conversation on this site... This is beyond my Google-fu. – user194703 Jun 11 at 19:28
• @Davislor -- I won't look for a thread, but I can tell you that, in pure mathematics, variables (usually lightface italic) may have defined variants in upright bold, bold italic, or several other alphabetic forms. For this reason, variables in otherwise bold titles and headings are not made bold in order to avoid changing the meaning. – barbara beeton Jun 11 at 22:23