\bf in the first argument of \cdot; causes the whole expression to become bold

Question

I want just the first argument in bold, but when i try to select just the first argument using the \bf command it modified the whole expression. This is what I had

\[
a = \frac12 \cdot \frac13 + \frac14  \\
\]

I just wanted \frac12 in bold so I used

\[
a = \bf{\frac12} \cdot \frac13 + \frac14  \\
\]

But this modified all the expression in bold.

Any clue how to solve this?

Welcome to TeX.SX! Please help us to help you and add a minimal working example (MWE) that illustrates your problem. It will be much easier for us to reproduce your situation and find out what the issue is when we see compilable code, starting with \documentclass{...} and ending with \end{document}. — , Sep 16 '14 at 20:40
@ChristianHupfer \frac12 is short for \frac{1}{2}, because argument braces can be dropped, if the argument consists of one token only. — Heiko Oberdiek, Sep 16 '14 at 20:43
@HeikoOberdiek: I know that, but's no nice use of the command ;-) — , Sep 16 '14 at 20:43
Note that \bf does not take an argument: It is a switch. That's why the entire remainder of the equation is set in bold. — Mico, Sep 16 '14 at 21:03

score 6 · Accepted Answer · answered Sep 16 '14 at 20:42

6

\bf is deprecated since LaTeX2e. Now \bfseries should be used in text mode. Both are commands that never take an argument, they remain active until the end of the current group or overwritten by another font switch command.

In math mode there are other options. Here \mathbf will do:

\documentclass{article}
\begin{document}
\[ a = \mathbf{\frac12} \cdot \frac13 + \frac14 \]
\end{document}

answered Sep 16 '14 at 20:42

Heiko Oberdiek

271,626

So what is the diference of using \textbf and \bfseries in text mode, besides the remaining of being active until the end of the current group? – JuanMuñoz Sep 16 '14 at 21:09
@JuanMuñoz \bfseries is the switch equivalent of \bf. If you want a limited bold face effect you plugin as an argument to \textbf{This text is bold.} This is not – percusse Sep 16 '14 at 21:56

\bf in the first argument of \cdot; causes the whole expression to become bold

1 Answers1