# Right way for text inside math

I'd like to know (if there is) the better way to punctuate text inside math mode. I mean, when we use , or ;, they are punctuation for the text, not for the math and so I think that they should be typed with the same font used for the text.

Consider the (non sense) example below. Please, note the font for , and the way I inserted blank space after it inside the sets.

Which one would you use?

MWE

\documentclass{report}
\usepackage{amsthm,amsmath,amssymb,amsfonts}
\usepackage[a5paper,margin=2cm]{geometry}
\newtheorem{thm}{Theorem}
\begin{document}

\begin{thm}Statement here in italic font. Then:
\begin{align*}
a_n&=
\begin{cases}
n+1, & \text{for odd $n$},\\
n+2, & \text{for even $n$}.
\end{cases}
\\[1ex]
a_n&=
\begin{cases}
n+1, & \text{for odd $n$,}\\
n+2, & \text{for even $n$.}
\end{cases}
\end{align*}
Also, let
$A= \{a_n,\ \text{for any$n>30$}\}$,
$A'= \{a_n, \text{ for any$n>40$}\}$ and
$A''=\{a_n \text{, for any$n>50$}\}$.
\end{thm}
\end{document}


• How about Also, let $A= \{a_n$ for any $n>30\}$ ? – Holene Apr 16 '15 at 7:51
• @Sigur - I've reopened the posting. You may want to edit it a bit to remove any ambiguity as to what the posting is about -- I suspect I'm not the only one who got stuck on the suboptimal use of \text. – Mico Apr 16 '15 at 9:11
• I consider something like $A= \{a_n,\ \text{for any$n>30$}\}$ simply wrong notation; $A=\{a_n:n>30\}$ would be right. – egreg Apr 16 '15 at 10:29
• I'd probably write $A=\{\text{$a_n$, for any$n > 30$}\}$ – Siminore Apr 16 '15 at 10:37
• in "traditional" (i.e., metal) math composition, all punctuation in theorems was upright, so it would be uniform whether in a math or a text context. there really should be a "theorem" font set up in this way, but that is a real pain, and it has never been done. – barbara beeton Apr 16 '15 at 19:06