\dagger我想从打印一些特殊符号（例如） tx-math.tex，但是在使用方面遇到了问题。
这是我的最小文档：
\input opmac
\chyph
\input lmfonts
\input tx-math.tex
\dagger
\bye
命令输出pdfcsplain test：
This is pdfTeX, Version 3.14159265-2.6-1.40.19 (TeX Live 2018) (preloaded format=pdfcsplain)
restricted \write18 enabled.
entering extended mode
encTeX v. Jun. 2004, reencoding enabled.
(./test.tex The format: csplain <Apr. 2016>.
The cs-fonts are preloaded and A4 size implicitly defined.
The utf8->iso8859-2 re-encoding of Czech+Slovak alphabet activated by encTeX
(/usr/local/texlive/2018/texmf-dist/tex/csplain/opmac/opmac.tex
This is OPmac (Olsak's Plain macros), version <Aug. 2018>
(/usr/local/texlive/2018/texmf-dist/tex/csplain/fonts/ams-math.tex
FONT: AMS math fonts - \mathchardef's prepared, 12 math families preloaded.)
The \^, \`, \', \v, \" and \r expands to characters by ISO-8859-2.)
cs hyphenation used (\language=5). \frenchspacing is set on.
(/usr/local/texlive/2018/texmf-dist/tex/csplain/fonts/lmfonts.tex
(/usr/local/texlive/2018/texmf-dist/tex/csplain/fonts/ff-mac.tex)
FONT: Latin Modern - {\caps \sans \ttset \slant \nbold \ttprop \ttlight \ttcond
\quotset \upital \dunhill } {\rm \bf \it \bi } +AMS
(/usr/local/texlive/2018/texmf-dist/tex/csplain/fonts/chars-8z.tex))
(/usr/local/texlive/2018/texmf-dist/tex/csplain/fonts/tx-math.tex
FONT: TX math fonts - \mathchardef's prepared, 14 math families preloaded.)
! Missing $ inserted.
<inserted text>
$
<to be read again>
\dagger
l.7 \dagger
?
哪里有问题？