Why is the \bf command applied to more than I asked?
Because \bf
is a (deprecated) switch that is turned on. It doesn't take an argument in the form \bf{x}
, but should rather be used {\bfseries x}
(instead of {\bf x}
. See Does it matter if I use \textit
or \it
, \bfseries
or \bf
, etc. and
Will two-letter font style commands (\bf
, \it
, …) ever be resurrected in LaTeX?
Instead, use \boldsymbol
(from amsmath
) or \mathbf
:
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\[ x(t), \boldsymbol{x}(t), \mathbf{x}(t), \boldsymbol{x(t)}, \mathbf{x(t)} \]
\end{document}
Use \bm
instead of \bf
. And \[...\]
instead of $$...$$
.
\documentclass{article}
\usepackage{bm}
\begin{document}
\[x(t), \bm{x}(t), \bm{x(t)}\]
\end{document}