# Underline at the same level

I want to underline alpha's and beta's, but at the same level. I mean, I don't want but . Maybe there is already a command that make it but I couldn't find it. The second image was obtained with the following command :

$\newlength{\espa} \settowidth{\espa}{$\alpha$}\rlap{\underline{\hspace{\espa}}}\alpha, \settowidth{\espa}{$\beta$}\rlap{\underline{\hspace{\espa}}}\beta$


which is hardly working but not totally. In normal math mode, no pbm. In scriptsize (or tiny or anything else) math mode, no pbm. But if I am in math mode within an exponent, then the \settowidth command does not seem to take into account that I am in sciptsize mode and, as a matter of fact, the underline is too long (e.g. ).

Any idea ?

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Would incorporating a \strut help to put all underlines at the same level? –  Christian Lindig Mar 24 '11 at 11:12
A \mathstrut would be more appropriate, assuming math mode is where you want to do it. It will scale with (sub)subscripts, which the regular \strut won't do. –  Harald Hanche-Olsen Mar 24 '11 at 12:08

$\underline{\smash{\beta}}$

Excellent! I have one question though: how can I achieve that the line of \underline{mytext} has the same width as mytext? –  Leon Jul 29 '11 at 3:36
Yes, in my case, the line of \emph{\underline{\smash{Proof}}}: is shorter than the word Proof. I was hoping there was some option to set the additional width manually, like \underline[2pt]{...} or something like that... –  Leon Jul 29 '11 at 18:11
@Leon: Ah. Unrelated to this question, really. But what you need is an italic correction: \emph{\underline{\smash{Proof\/}}}:. Or better yet, restructure your usage to allow \emph to do its job of adding italic correction automagically: \underline{\emph{Proof}}:. –  Harald Hanche-Olsen Jul 30 '11 at 9:14