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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}

enter image description here

Sigur
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  • How about Also, let $ A= \{a_n$ for any $n>30\}$ ? – Holene Apr 16 '15 at 07:51
  • @Holene, this is not a good idea. It will not work for displaystyle, for example. – Sigur Apr 16 '15 at 08:00
  • I would use \textnormal instead of \text. – Mico Apr 16 '15 at 08:44
  • @Mico, I checked the definition of \textnormal now but I can not see what would change. Is it simple to have an example? – Sigur Apr 16 '15 at 08:49
  • Assuming the "normal" text font (outside the theorem-like environment...) is an upright roman font, \textnormal will render its argument in the same upright roman font. If the "normal" text font is an upright sans-serif, \textnormal will pick up on that too. – Mico Apr 16 '15 at 08:57
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    @Sigur - I voted to close this posting based on the part of your question related to the \text instruction. If your posting is really more about the placement of puctuation marks, please let me know and I'll vote to reopen to the posting. – Mico Apr 16 '15 at 09:00
  • @Mico, I was reading the post you cited but it is not the same. My problem is where to insert the commas: in math or text mode. Also, the spaces after them: using \ in math mode or blank spaces in text mode? Please, could you reopen it? – Sigur Apr 16 '15 at 09:04
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    @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 09:11
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    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
  • @egreg, I agree. It was only a dummy example. What I need is to write some textual parts inside some math contents, since it would be complicated to write using only symbols. – Sigur Apr 16 '15 at 10:34
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    I'd probably write $A=\{\text{$a_n$, for any $n > 30$}\}$ – Siminore Apr 16 '15 at 10:37
  • @egreg, what about the comma after n+1? Should it be in italic? – Sigur Apr 16 '15 at 11:23
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    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

0 Answers0