🚀 go-pugleaf

Hi,

While I was preparing a handout for Logic students, I had two write
the following formula with the underbraces (consider lines as
undebraces, it is difficult to simulate them using characters):

((P --> Q) v (P -->R)) --> (P --> (Q & R))
                                   -   -
                                   F   T
                            -     -------
                            T        F
----------------------     ---------------
          T                       F

Using,

$\underbrace{((P \rightarrow Q) \vee (P \rightarrow R))}_{T}
\rightarrow \underbrace{(\underbrace{P}_{T} \rightarrow 
\underbrace{(\underbrace{Q}_{F} \wedge \underbrace{R}_{T})}_{F})}_{F}$

I get,

((P --> Q) v (P -->R)) --> (P --> (Q & R))
----------------------      -      -   -
           T                T      F   T
                                  -------
                                     F
                           ---------------
                                  F

as  expected (note the  difference between the  "heights" of the first
two underbraces of the result and my  intent).  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?

-- 
| Mr. Tuna Ertemalp        | Mailbox #659            | Small things together |
| Stanford University      | Crothers Memorial Hall  |   form the quality,   |
| Computer Science MS      | Stanford, CA 94305, USA | But quality is not a  |
| Ertem@Polya.Stanford.Edu | (415) 328-8515          |     small thing!      |