bm: Individual bold math symbols

Specifying \boldmath is the best method for typesetting a whole math expression in bold. But to typeset individual symbols within an expression in bold, the bm package provided by the LaTeX Project team is better. Its usage is outside the scope of this document (see its documentation at https://ctan.org/pkg/bm or in your installation) but the spacing in the output of this small example will show that it is an improvement over \boldmath within an expression:

\usepackage{bm}   % in preamble
we have $\bm{v} = 5\cdot\bm{u}$

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