manually controlling height of the horizontal line of the radix or root symbol

Question

While using lucida fonts, I have big problems with the height of the horizontal line of the radix or root symbol. Sometimes \[ \sqrt[x^2 + x} \] comes out allright, but for example, in a fraction \[ \frac{x^2 + x}{x^2 + x} \], the exponents "2" stick literally to the horizontal radix line. I tried to fix that using a vertical strut

$\newcommand{\S}{\rule[0pt]{0pt}{1.6 ex}}$  

and variants of it and write

\[ \frac{ \sqrt{\S x^2 + x} }{ \sqrt{\S x^2 + x} } \] 

but this does not help. Does anyone have better ideas?

Answer 1

With the Lucida Math font (for pdflatex), here's what I get from the following code

\documentclass{article}
\usepackage{amsmath}
\usepackage{lucimatx}

\begin{document}

\[ \frac{ \sqrt{x^2 + x} }{ \sqrt{x^2 + x} } \]

\[ \frac{ \sqrt{\mathstrut x^{2} + x} }{ \sqrt{x^{\mathstrut 2} + x} } \]

\end{document}

I don't find the first display particularly squashed together; the impression might be given when looking at the result at low resolution (that is, on the screen without magnification).

In the second display I suggest two (manual) methods for obtaining more room.

If I use the OpenType version, I get from

\documentclass{article}
\usepackage{amsmath}

\usepackage{unicode-math}
\setmathfont{Lucida Bright Math OT}

\begin{document}

\[ \frac{ \sqrt{x^2 + x} }{ \sqrt{x^2 + x} } \]

\end{document}

the following picture, which shows perhaps better spacing.