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From: dlau@cs.utexas.edu (David Lau)
Newsgroups: comp.text
Subject: Re: Underbraces in LaTeX
Message-ID: <4579@cs.utexas.edu>
Date: 16 Jan 89 08:02:24 GMT
References: <6124@polya.Stanford.EDU>
Organization: U. Texas CS Dept., Austin, Texas
Lines: 21

In a previous article, ertem@polya.Stanford.EDU (Tuna Ertemalp) wrote:

>>                                          ....  Is there any trick (or
>>something I  missed  in the book)   which  could  make it  possible to
>>specify the "height"   of   the underbrace   with respect   to   other
>>underbraces, or have unvisible underbraces?

The trick is you have to fool TeX into thinking that both sides of the
logical expressions have the same depth:

\newsavebox{\lhs}\newsavebox{\rhs}%
\sbox{\rhs}{$(\underbrace{Q}_F \wedge \underbrace{R}_T)$}%
\sbox{\lhs}{$P$}%
\dp\lhs=\dp\rhs % <-- fake box depth
\sbox{\rhs}{$(\underbrace{\usebox{\lhs}}_T\rightarrow\underbrace{\usebox{\rhs}}_F)$}%
\sbox{\lhs}{$((P\rightarrow Q) \vee (P\rightarrow R))$}%
\dp\lhs=\dp\rhs % <-- same as before
$\underbrace{\usebox{\lhs}}_T\rightarrow\underbrace{\usebox{\rhs}}_F$


--David (dlau@cs.utexas.edu)