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I have an equation where the nabla symbol should be the same height as the fraction. Instead, it's about half the height. How do I fix this?

Wrong sized nabla symbol

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  • Are you sure that the nabla symbol should actually extend in size? – CampanIgnis May 9 '20 at 16:44
  • nabla is a letter not a stretchy symbol, as the images in the answers below show it will look really quite odd if you scale it. – David Carlisle May 9 '20 at 17:56
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Not sure this looks the best, but you did ask to scale \nabla to the fraction height. scalerel does this:

\documentclass{beamer}
\usepackage{mathtools}
\DeclarePairedDelimiter{\norm}{\lVert}{\rVert}
\usepackage{scalerel}
\begin{document}
\begin{frame}
\[
\scalerel{\nabla}{\frac{\norm{F(q) - D}^2}{2\norm{D}^2\sigma^2}}
\]
\end{frame}
\end{document}

enter image description here

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  • 2
    that is really quite painful to behold:-) – David Carlisle May 9 '20 at 17:55
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    @DavidCarlisle Yes it is, but as they say in the world of retail business, "the customer is always right!" – Steven B. Segletes May 9 '20 at 18:08
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    @DavidCarlisle Given the upvotes, I can only conclude there is a grotesque fascination with it, sort of like how traffic slows down to rubberneck at accident scenes. – Steven B. Segletes May 9 '20 at 21:39
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    I'm sure you will be relieved to know that my honour is intact and I didn't vote for you:-) – David Carlisle May 9 '20 at 21:43
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    Thanks a bunch. It does look odd. Unfortunately I have my own "customer" for this ;) – Georgia S May 11 '20 at 14:00
1

If you want to set the scaling yourself you can use \scalebox, combined with \raisebox to position the symbol vertically.

But as noted in the other answers this is not really a good idea, the symbol should have a 'normal' height of one line and not be twice as big as the other symbols.

\documentclass{beamer}
\usepackage{amsmath}
\usepackage{graphicx}
\begin{document}
\begin{frame}{}
% change the 2 in \scalebox{2} to influence the amount of scaling
% change the -4pt in \raisebox{-4pt} to influence the vertical position
$\raisebox{-4pt}{\scalebox{2}{$\nabla$}}\frac{\lVert F(q)-D\rVert^2}{2\lVert D\rVert^2\sigma^2}$
\end{frame}
\end{document}

enter image description here

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It is no surprise that \nabla does not get bigger beside the fraction: this symbol is not supposed to scale, usually. However, it can be enlarged manually using larger font sizes. To do that easily, you could use the command \mathlarger from the relsize package. They can be nested to get bigger font sizes.

\documentclass{beamer}
\usepackage{mathtools}
\usepackage{relsize}
\DeclarePairedDelimiter{\norm}{\lVert}{\rVert}
\newcommand{\mathllarger}[1]{\mathlarger{\mathlarger{#1}}}
\newcommand{\mathlllarger}[1]{\mathlarger{\mathlarger{\mathlarger{#1}}}}
\newcommand{\mathllllarger}[1]{\mathlarger{\mathlarger{\mathlarger{\mathlarger{#1}}}}}
\begin{document}
\begin{frame}
1 step:
\[
\mathlarger{\nabla}\frac{\norm{F(q) - D}^2}{2\norm{D}^2\sigma^2}
\]
2 steps:
\[
\mathllarger{\nabla}\frac{\norm{F(q) - D}^2}{2\norm{D}^2\sigma^2}
\]
3 steps:
\[
\mathlllarger{\nabla}\frac{\norm{F(q) - D}^2}{2\norm{D}^2\sigma^2}
\]
4 steps:
\[
\mathllllarger{\nabla}\frac{\norm{F(q) - D}^2}{2\norm{D}^2\sigma^2}
\]
\end{frame}
\end{document}

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