Large vertical spacing in denominator above \rho

Question

The vertical spacing above rho in the denominator here is off. I'm not sure if it's caused by the descender in the numerator, or if that only exaggerates the issue. I think both 2/μ and μ/2 look alright, but I'm not a typographer. How can I make it look proper?

\documentclass{article}
\begin{document}
\begin{equation}
  \sqrt{\frac2\rho} + \sqrt{\frac\mu\rho} + \sqrt{\frac\mu2}
\end{equation}
\end{document}

Answer 1

You can raise the \rho, but I wouldn't. making one isolated term look "better" at the expense of losing consistent baselines is not usually a good trade, but...

\documentclass{article}
\begin{document}
\begin{equation}
  \sqrt{\frac{2}{\rho}} +
  \sqrt{\frac{\mu}{\rho}} +
  \sqrt{\frac{\mu}{\raisebox{2pt}[0pt]{$\rho$}}} +
  \sqrt{\frac{\mu}{2}}
\end{equation}
\end{document}

Answer 2

In the OP's code, the three square root symbols don't have the same height (and depth too, for that matter). IMNSHO, the sum would look a whole lot better if the three square root symbols had the same size. I suggest you change of numerator of the middle term from \mu to \mu\vphantom{2}.

\documentclass{article}
\begin{document}
\[
\sqrt{\frac{2}{\rho}} + \sqrt{\frac{\mu}{\rho}} + \sqrt{\frac{\mu}{2}}
\quad{\mbox{vs.}}\quad
\sqrt{\frac{2}{\rho}} + \sqrt{\frac{\mu\vphantom{2}}{\rho}} + \sqrt{\frac{\mu}{2}}
\]
\end{document}

---

Addendum: The OP has provided a comment with information about the "real" expression of interest, viz., c_\text{sh}=\sqrt{\frac\mu\rho}, and has asked what kind of placement corrections (if any) I'd apply to this expression.

• My main recommendation would be to switch from \frac notation to inline-fraction notation, i.e., to write \sqrt{\mu/\rho}. This works especially well because \mu and \rho happen to have the same height and depth.

• If \frac notation cannot be avoided, I'd say that it's the vertical placement of the square root symbol that's the real issue here, rather than the placement of the denominator term in the fraction. Compare \sqrt{\frac{\mu}{\rho}} against \sqrt{\frac{\mu}{\smash[b]{\rho}}}: IMNSHO, the latter expression looks better because while the tall square root symbols have the same overall size in both cases, the square root symbols is placed a bit higher in the latter case, leading to better overall proportions.

Oh, and I'd write c_{\mathrm{sh}} rather than c_{\text{sh}}.

\documentclass{article}
\usepackage{amsmath} % for \smash[b] macro
\begin{document}
\[
c_{\mathrm{sh}}=\sqrt{\frac{\mu}{\rho}}
               =\sqrt{\frac{\mu}{\smash[b]{\rho}}}
               =\sqrt{\mu/\rho}
\]
\end{document}