LaTeX Latex Vector Notation: Writing Vectors in Bold and Using Arrows - Tips & Tricks

AI Thread Summary
To write vectors in LaTeX, using \mathbf for bold formatting can lead to unintended bolding of other symbols, such as GM_1, so it is recommended to use \boldsymbol instead for proper vector notation. The use of \textbf in math mode is discouraged as it can produce undesirable results. For arrows instead of bold notation, the \vec command is suggested, with the option to create a custom macro for flexibility in formatting. This allows for easy switching between bold and arrow representations without altering the entire document. A LaTeX guide is also available for further assistance.
IlyaZ
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Homework Statement


a. How do I write vectors bold within displaymath and frac. I want Phi, r and r_1 bold. But get G M_1 bold as well = bad.
b. How do I use arrows instead of the bold notation?

The Attempt at a Solution


\begin{displaymath}
a1. textbf{\Phi(r)} = -\frac{G M_1}{| textbf{r}-textbf{r_1} |}
\end{displaymath}
a2. \bf{\Phi}(\bf{r}) = -\frac{G M_1}{| \bf{r}-\bf{r_1} |}
 
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Arrows: \vec : \vec \Phi ( \vec r) = -\frac{G M_1}{| \vec{r}-\vec r_1 |}
Bold: \mathbf : \mathbf{\Phi}( \mathbf{r}) = -\frac{G M_1}{| \mathbf{r}-\mathbf{r_1} |}

I don't think you really want the potential to be a vector, but that's what your code implied, so I kept it.
 
Last edited:
IlyaZ said:
a. How do I write vectors bold within displaymath and frac. I want Phi, r and r_1 bold. But get G M_1 bold as well = bad.

You get other bad stuff as well using \textbf. Don't use it in math mode.

\textbf{\Phi(r)} = -\frac{G M_1}{| \textbf{r}-\textbf{r_1} |}
\textbf{\Phi(r)} = -\frac{G M_1}{| \textbf{r}-\textbf{r_1} |}

\bf doesn't work at all:
\bf{\Phi}(\bf{r}) = -\frac{G M_1}{| \bf{r}-\bf{r_1} |}
\bf{\Phi}(\bf{r}) = -\frac{G M_1}{| \bf{r}-\bf{r_1} |}

Timo suggested \mathbf, but that doesn't work on some things.
If you have access to the AMSLaTeX macros, (and you should), use \boldsymbol.

\boldsymbol{\Phi}(\boldsymbol{r}) = -\frac{G M_1}{| \boldsymbol{r}-\boldsymbol{r}_1 |}
\boldsymbol{\Phi}(\boldsymbol{r}) = -\frac{G M_1}{| \boldsymbol{r}-\boldsymbol{r}_1 |}

b. How do I use arrows instead of the bold notation?

Use \vec.

An even better solution is to define your own vector macro that formats vectors the way you want them to appear. For example,
\newcommand{\vect}[1]{\boldsymbol{#1}}


Then when someone tells you to format your vectors with arrows instead you can simply change that one macro.
\newcommand{\vect}[1]{\vec{#1}}

Bold symbols are used for things other than vectors (matrices, for example). A global search-and-replace is not a good idea.
 

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