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i want to Write sub-and superscript in math mode but not italic. 

 \documentclass[a4paper,11pt]{article}
        \usepackage{amsmath}
        \begin{document}
            % using mathmode sub- and supperscrit.
 \begin{equation}
\mathbf{M}^{T}
\end{equation}
\begin{equation}
\mathbf{M}_{xx}
\end{equation}
        % I can do it using /bf but it makes it is also bold.

        \begin{equation}
\bf{M}^{T}
\end{equation}

\begin{equation}
\bf{M}_{xx}
\end{equation}
        \end{document}
user31177
  • 1,089
  • Have you tried \rm instead of \bf? Incidentally, you mention material in subscripts and superscripts; what about the material in the "normal" positions? Should that material be rendered in (math) bold automatically? – Mico Apr 26 '16 at 16:04
  • (1) \bf is a switch, thus does not take arguments, (2) \bf switches to the text font, not wat you want, (3) either use \mathbf or (IMO better) load the bm package and use \bm{M} as it will be bold and italic mah font – daleif Apr 26 '16 at 16:13
  • @Mico, infact it is equation environment. – user31177 Apr 26 '16 at 16:39

1 Answers1

2

If you want to display material in sub- and superscripts using roman/upright rather than italic letters, you should render the main material (i.e., what's on the main math axis) using roman/upright letters as well.

One way to render all math material with upright letters on a document-wide basis is to load the mathastext package:

\usepackage{mathastext}

Another method for achieving this look on a document-wide basis would be to issue the instructions

\everymath{\rm}
\everydisplay{\rm}

in the preamble.

Addendum: The commands \bf and \rm are considered deprecated in LaTeX2e documents. They do happen to work -- more or less as one would expect they should work in a Plain-TeX document -- if one uses one of the "standard" LaTeX document classes (article, report, and book) or a document class that's based on one of the standard classes. If you use one of the Koma-Script document classes, though, you'll get a warning message. Finally, \bf and \rm aren't defined at all in the memoir document class. For general portability of one's code across document classes, the \bm and \rm macros shouldn't be used in a LaTeX document anymore.

Mico
  • 506,678
  • \rm should warrant a downvote. – egreg Apr 26 '16 at 16:40
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    @egreg - Why? As explained in more detail in this answer, the standard LaTeX classes define \rm as follows: \DeclareOldFontCommand{\rm}{\normalfont\rmfamily}{\mathrm}. Thus, \rm in math mode acts like \mathrm. – Mico Apr 26 '16 at 16:47
  • Try that with memoir ;-) – daleif Apr 26 '16 at 16:48
  • I didn't downvote, but I won't upvote either. This is wrong. But, since the upshape characters chosen by \mathrm generally correspond to family 0, you should know what to do. – egreg Apr 26 '16 at 16:48
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    @daleif - The OP used the article class in the MWE. This made me think it's OK to use a definition of \rm that is provided by the article class. – Mico Apr 26 '16 at 16:49
  • @egreg - My preference, for sure, would be to use the mathastext package. – Mico Apr 26 '16 at 16:51
  • I still agree with egreg users should not be encouraged to use \rm in latex, plus doesn't it still give you a warning in article? – daleif Apr 26 '16 at 16:52
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    @daleif - \sc and \sl in math mode will generate a LaTeX warning, but \rm, \bf, \sf, \tt, and \it do not. – Mico Apr 26 '16 at 16:55
  • Oh, didn't know that, odd. – daleif Apr 26 '16 at 16:56