size and location of cube root symbol [duplicate]

Possible Duplicate:
Nice-looking p-th roots

On math.stackexchange I wanted the cube root of a fraction in display mode, and used $$\sqrt[3]{\frac ab}$$ to get it. The 3 comes out very small and low in the root sign. I also thought of $$^3\sqrt{\frac ab}$$ but the 3 comes out too far to the left.

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marked as duplicate by Peter Grill, percusse, lockstep, Martin Schröder, Marco DanielAug 16 '12 at 14:14

@PeterGrill: Thanks. I searched for a while to try to find something like that, but didn't. –  Ross Millikan Aug 14 '12 at 0:27
Yeah, things are not always easy to find here. I only knew it exited as I had asked a follow up question: Using \leftroot{}, \uproot{} with closed square root symbol where I had referenced that question. –  Peter Grill Aug 14 '12 at 0:29

You can use \leftroot (for horizontal shifting), and/or \uproot (for vertical shifting) from the amsmath package; using \scriptstyle you can increase the size of the index (not sure if this is a good idea); preferable to use a superscript instead of the root:

\documentclass{article}
\usepackage{amsmath}

\begin{document}

$\sqrt[3]{\frac{a}{b}}\qquad \sqrt[\leftroot{-1}\uproot{2}\scriptstyle 3]{\frac{a}{b}}\qquad \Bigl(\frac{a}{b}\Bigr)^{1/3}$

\end{document}


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Works great. Thanks. –  Ross Millikan Aug 13 '12 at 17:23