"platex" is a command used by Japanese-tex user. I'm sorry. There was two-byte blanks in my tex source ,though they aren't apparent in my e-mail. When I removed them, everything was OK. Below is a log when compiling a tex source with two-byte blanks.
$ platex 3.tex This is e-pTeX, Version 3.14159265-p3.5-130605-2.6 (utf8.euc) (TeX Live 2015/dev/Debian) (preloaded format=platex) restricted \write18 enabled. entering extended mode (./3.tex pLaTeX2e <2006/11/10> (based on LaTeX2e <2014/05/01> patch level 0) Babel <3.9l> and hyphenation patterns for 11 languages loaded. (/usr/share/texlive/texmf-dist/tex/latex/base/article.cls Document Class: article 2014/09/29 v1.4h Standard LaTeX document class (/usr/share/texlive/texmf-dist/tex/latex/base/size10.clo)) (/usr/share/texlive/texmf-dist/tex/latex/amsmath/amsmath.sty For additional information on amsmath, use the `?' option. (/usr/share/texlive/texmf-dist/tex/latex/amsmath/amstext.sty (/usr/share/texlive/texmf-dist/tex/latex/amsmath/amsgen.sty)) (/usr/share/texlive/texmf-dist/tex/latex/amsmath/amsbsy.sty) (/usr/share/texlive/texmf-dist/tex/latex/amsmath/amsopn.sty)) (/usr/share/texlive/texmf-dist/tex/latex/amsfonts/amssymb.sty (/usr/share/texlive/texmf-dist/tex/latex/amsfonts/amsfonts.sty)) LaTeX Warning: Unused global option(s): [28pt,a4j]. (./3.aux) (/usr/share/texlive/texmf-dist/tex/latex/amsfonts/umsa.fd) (/usr/share/texlive/texmf-dist/tex/latex/amsfonts/umsb.fd) ! Not two-byte family. l.5 ( \alpha \in \mathbb{C} ) ? ! Not two-byte family. l.5 ( \alpha \in \mathbb{C} ) ? [1] (./3.aux) ) Output written on 3.dvi (1 page, 376 bytes). Transcript written on 3.log. Cheers, EenyMeenyMinyMoa 2016-06-09 10:56 GMT+08:00 EenyMeenyMinyMoa <eenymeenyminy...@gmail.com>: > Hi. > > \documentclass[28pt,a4j]{article} > \usepackage{amsmath,amssymb} > \begin{document} > \begin{eqnarray*} > ( \alpha \in \mathbb{C} ) > \end{eqnarray*} > \end{document} > > I compiled this tex source by > $ platex 3.tex > But unexpected \Gamma's as the attached file appeared. > Why? > > > Cheers, > EenyMeenyMinyMoa >