[texhax] fbox in align environment

[Sebastian Canagaratna]

Thanks, Phil. The first example works fine, but the second fails:

ERROR: Illegal unit of measure (mu inserted).

--- TeX said ---
<to be read again> 
                   =
l.13 \end{align}
                
--- HELP ---
If you just got a

      ! Missing number, treated as zero.

error, then this is part of the same problem.

Perhaps I did something wrong, I'll investigate it and let you know.

Thanks again.

Sebastian

On Mon, Jun 15, 2009 at 10:29:06AM +0200, Philip G. Ratcliffe wrote:
> > Say you have three equations in an align environment. You 
> > want to box only one of them, say the last one. How does one 
> > do this? I want all three equations aligned (at, say the = 
> > sign). Fancybox.sty wasn't of much help in this regard. I can 
> > put the first two eqns in an align, and the third eqn in an 
> > fbox in the equation environment, but the alignment is disturbed. 
> 
> If you haven't found anything better, here's a not very elegant solution:
> 
> \documentclass{article}
> \usepackage{amsmath}
> \newcommand\alignboxed[2]{\rlap{\boxed{#1#2}}\hphantom{#1\mkern6mu}}
> \begin{document}
> \begin{align}
>   f_1(x) &= a+bx, \\
>   f_2(x) &= a+bx+cx², \\
>   \alignboxed{f_3(x)}{= a+bx+cx²+dx³.}
> \end{align}
> \end{document}
> 
> This works similarly:
> 
> \documentclass{article}
> \usepackage{amsmath}
> \def\alignboxed#1&#2\endalignboxed{\rlap{\boxed{#1#2}}\hphantom{#1\mkern6mu}
> }
> \begin{document}
> \begin{align}
>   f_1(x) &= a+bx, \\
>   f_2(x) &= a+bx+cx², \\
>   \alignboxed
>   f_3(x) &= a+bx+cx²+dx³.
>   \endalignboxed
> \end{align}
> \end{document}
> 
> Cheers,  Phil
>