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enter image description here

In a physics textbook I met an equation, as in Figure above, with the bold upright greek letter β.

How could I edit equations that contain such characters in boldface?

closed as off-topic by Mico, user31729, Kurt, barbara beeton, Claudio Fiandrino May 7 '16 at 15:42

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    Those are Lorentz transformation equations for non-standard orientation of the frame of references, I assume? – user31729 May 7 '16 at 13:13
  • @ Christian Hupfer : Yes, exactly ! – Frobenius May 7 '16 at 13:15
  • I would define a command \vec that would check if its argument is certain letters and output conveniently what you want them to look, so \vec a \vec \beta \vec x would be converted to \mathbf{a} \bm{\upbeta} \mathbf{x}, for instance. – Manuel May 7 '16 at 13:20
  • @Manuel : please read my first comment in Christian Hupfer's answer to see where I'm interesting to use it for. – Frobenius May 7 '16 at 13:26
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    I'm voting to close this question as off-topic because the OP is interested in a Mathjax-only solution. – Mico May 7 '16 at 13:55
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Try the upgreek package and \boldsymbol from amsmath (or mathtools.

\documentclass{article}

\usepackage{mathtools}
\usepackage{upgreek}

\begin{document}

\begin{align}
 x'_{0} &= \gamma \left( x_{0} - \boldsymbol{\upbeta \cdot x}\right) \\
 \boldsymbol{x}' &= \boldsymbol{x} + \dfrac{\gamma-1}{\boldsymbol{\upbeta}^2}  \left( \boldsymbol{\upbeta \cdot x}\right)\boldsymbol{\upbeta} - \gamma \boldsymbol{\upbeta} x_{0} 
\end{align}

\end{document}

enter image description here

  • Thanks, but how can I edit upgreek in bold in an equation written inside an answer or a question in Physics SE, for example therein : physics.stackexchange.com/questions/254501/… – Frobenius May 7 '16 at 13:12
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    @Frobenius: You're after MathJaX stuff? This is not on-topic here! – user31729 May 7 '16 at 13:14
  • @ Christian Hupfer : Anyway, thanks for the answer. – Frobenius May 7 '16 at 13:16
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The screenshot you've posted suggests you're interested in Times Roman-based Fonts. If that's the case, I suggest you load the newtxtext and newtxmath packages. The latter package, happily, provides "upright" lowercase Greek math symbols. They may be accessed by prefixing "up" to the macro for the ordinary symbol (e.g., \upalpha, \upbeta, etc.).

To typeset the right-hand curly brace that's shown in your screenshot, you could encase the two equations in an array environment, as is done in the code shown below. Alternatively, you could load the mathtools package and use a drcases environment.

Aside: I wouldn't typeset the \cdot symbol in bold unless \boldsymbol{\cdot} really is supposed to differ meaningfully from \cdot. And, if you have a lot of instances of "\boldsymbol{\upbeta}", you may want to define a shortcut macro--say, \newcommand\bupbeta{\boldsymbol{\upbeta}}--to simplify the keyboarding of your document.

\documentclass{article}
\usepackage{newtxtext,newtxmath,array}

\begin{document}
\[
\setlength\arraycolsep{0pt}
\left. \begin{array}{r @{{}={}} >{\displaystyle}l }
x'_0 & \gamma ( x_0^{} - \boldsymbol{\upbeta} \cdot \mathbf{x}) \\[1ex]
\mathbf{x}' & \mathbf{x}+\frac{(\gamma-1)}{\beta^2}
    (\boldsymbol{\upbeta} \cdot \mathbf{x})\boldsymbol{\upbeta}
    -\gamma\boldsymbol{\upbeta}x_0^{}
\end{array}\right\}
\]
\end{document}

enter image description here

  • Many thanks for your answer, but I realize that my question is off-topic here since it's about MathJax stuff, please see comments in Christian Hupfer's answer. – Frobenius May 7 '16 at 13:43
  • Although my question is off-topic, your answer is very valuable for me to use in documents I edit for my own pleasure with LaTeX. – Frobenius May 7 '16 at 18:12
  • @Frobenius - Feel free to modify your posting so that MathJax is no longer an important aspect. – Mico May 7 '16 at 18:38

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