# Which package is needed for \boldsymbol{}?

I am using \boldsymbol{} and \textit{}, but they are not recognized. The document preamble is the following:

\documentclass{book}
\usepackage[spanish]{babel}
\selectlanguage{spanish}
\usepackage[utf8]{inputenc}
\setcounter{tocdepth}{4}
\setcounter{secnumdepth}{4}
\usepackage{parskip}
\usepackage{graphicx}
\usepackage{multirow}
\usepackage{amsmath, calc}
\usepackage[margin=1.5in]{geometryit is}
\usepackage{hyperref}
\usepackage{textcomp}
\usepackage{listings}
\usepackage[svgnames]{xcolor}
\usepackage{fontspec}
\usepackage{mathptmx}
\usepackage[nottoc,notlot,notlof]{tocbibind}
\usepackage[numbers]{natbib}
\begin{document}

For example, I'm using $\boldsymbol{x}_t$ and
\textit{vector de estados} within a paragraph.

\end{document}


Which lines concern the font or the commands that are not working? What should I change?

• You have an issue with \usepackage[margin=1.5in]{geometryit is}... that's completely irrelevant to your question, but it remains a problem. – Werner Dec 13 '17 at 22:53
• It should be \usepackage[margin=1.5in]{geometry} since there's no package called geometryit is. – Werner Dec 13 '17 at 22:57
• In answer to your question, \textit is available by default and \boldsymbol is supplied by amsmath (even though \bm from bm is a suggested improvement/alternative). – Werner Dec 13 '17 at 22:58
• But if I'm using \usepackage{amsmath, calc}, why is \boldsymbol{} not working? And if \textit{} is default, why is it not working either? – Alfie González Dec 13 '17 at 22:59
• There's nothing that points to \textit being disable/unavailable based on your code snippet. So the problem must be somewhere else... – Werner Dec 13 '17 at 23:16

\documentclass{book}
\usepackage[spanish]{babel}
\selectlanguage{spanish}
\usepackage[utf8]{inputenc}
\setcounter{tocdepth}{4}
\setcounter{secnumdepth}{4}
\usepackage{parskip}
\usepackage{graphicx}
\usepackage{multirow}
\usepackage{amsmath, calc}
\usepackage[margin=1.5in]{geometry}
\usepackage{hyperref}
\usepackage{textcomp}
\usepackage{listings}
\usepackage[svgnames]{xcolor}
%\usepackage{fontspec}
\usepackage{mathptmx}
\usepackage[nottoc,notlot,notlof]{tocbibind}
\usepackage[numbers]{natbib}

\begin{document}

For example, I'm using $\boldsymbol{x}_t$ and \textit{vector de estados} within a paragraph.
\end{document}


mathptmx is very old and has no bold fonts, a better times clone is newtxmath

\documentclass{book}
\usepackage[spanish]{babel}
\selectlanguage{spanish}
\usepackage[utf8]{inputenc}
\setcounter{tocdepth}{4}
\setcounter{secnumdepth}{4}
\usepackage{parskip}
\usepackage{graphicx}
\usepackage{multirow}
\usepackage{amsmath, calc}
\usepackage[margin=1.5in]{geometry}
\usepackage{hyperref}
%\usepackage{textcomp}
\usepackage{listings}
\usepackage[svgnames]{xcolor}
%\usepackage{fontspec}
%\usepackage{mathptmx}
\usepackage{newtxtext,newtxmath}
\usepackage[nottoc,notlot,notlof]{tocbibind}
\usepackage[numbers]{natbib}

\begin{document}

For example, I'm using $\boldsymbol{x}_t$ and \textit{vector de estados} within a paragraph.
\end{document}


Please use the package bm in the preamble:

\usepackage{bm}


And in document use

\bm{}


For examples, bold symbols with italic shape are

$\bm{\alpha}=\bm{t}$


compared with them, the normal symbols are

$\alpha=t$


The compiled PDF for them would be

By the way,

• in fact \bm{} won't change any shape of symbols but only increase
the thickness of symbols.
• bm package can be used under every mathematical fonts, including mathptmx you used.
• bm can really only make acceptable output if there is a bold font available (it can use poor man's bold, overprinting three copies of the symbol with slight offsets, but that's not recommended) – David Carlisle Dec 14 '17 at 7:47
• Another reason to stick to boldsymbol is that the command is avaiblable by default in Mathjax, which comes in handy e.g. when writing documentation with Doxygen. – Rastapopoulos Feb 14 '18 at 17:08