Latex vector notation.

  1. 1. The problem statement, all variables and given/known data
    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?

    3. 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} |}
     
  2. jcsd
  3. Arrows: \vec : [tex]\vec \Phi ( \vec r) = -\frac{G M_1}{| \vec{r}-\vec r_1 |} [/tex]
    Bold: \mathbf : [tex]\mathbf{\Phi}( \mathbf{r}) = -\frac{G M_1}{| \mathbf{r}-\mathbf{r_1} |} [/tex]

    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: Sep 20, 2007
  4. D H

    Staff: Mentor

    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} |}
    [tex]\textbf{\Phi(r)} = -\frac{G M_1}{| \textbf{r}-\textbf{r_1} |}[/tex]

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

    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 |}
    [tex]\boldsymbol{\Phi}(\boldsymbol{r}) = -\frac{G M_1}{| \boldsymbol{r}-\boldsymbol{r}_1 |}[/tex]

    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.
     
  5. Thanks, that works great!
     
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