# Latex: Determinant

• Nov 24th 2008, 04:47 AM
Lucimeire83
Latex: Determinant
Hi

I'm trying to add some braces above/below and left/right of a Determinant to describe how many Columns and Rows certain ranges of the matrix has.
For example I have a 2 by 2 Block-matrix. I want a brace over the first and the one over the second column telling me how large each blockdeterminant is.

I hope someone knows a solution to this problem.

• Nov 24th 2008, 05:42 AM
Opalg
Plain TeX has a macro called \bordermatrix that lets you put labels above the columns and to the left of the rows. It can give you things like this:

$\displaystyle M = \bordermatrix{&\overbrace{}^{\textstyle m}&\overbrace{}^{\textstyle n}\cr p\{&A&B\cr q\{&C&D\cr}$

Code:

 M = \bordermatrix{&\overbrace{}^{\textstyle m}  &\overbrace{}^{\textstyle n}\cr  p\{ &A&B\cr q\{ &C&D\cr}
As far as I know, there is no LaTeX version of this, so you have to use the plain TeX syntax, with for example \cr instead of \\ for the carriage returns.
• Nov 24th 2008, 06:28 AM
Lucimeire83
OPALG, Thank you for your help, but I think that \bracematrix use just for matrix and I want to use for a determinant.
• Nov 24th 2008, 12:58 PM
Opalg
Ahem, yes. You'd think I might have noticed that very conspicuous bolded word Determinant (Doh)

So, the best I can do is a really ugly kludge that produces $\displaystyle \begin{array} {r|@{\hspace{9pt}}c@{\hspace{12pt}}c@{\hspace{9pt} }|} \multicolumn{3}{r@{\hspace{1pt}}}{\overbrace{}^{\t extstyle m} \overbrace{}^{\textstyle n}} \\ p\,\{&A&B\\ q\,\{&C&D \end{array}$.

Code:

\begin{array} {r|@{\hspace{9pt}}c@{\hspace{12pt}}c@{\hspace{9pt}}|} \multicolumn{3}{r@{\hspace{1pt}}}{\overbrace{}^{\textstyle m} \overbrace{}^{\textstyle n}} \\  p\,\{&A&B\\ q\,\{&C&D \end{array}
This has the drawback that it isn't well aligned vertically. If you want to put it in a formula like $\displaystyle M = \begin{array} {r|@{\hspace{9pt}}c@{\hspace{12pt}}c@{\hspace{9pt} }|} \multicolumn{3}{r@{\hspace{1pt}}}{\overbrace{}^{\t extstyle m} \overbrace{}^{\textstyle n}} \\ p\,\{&A&B\\ q\,\{&C&D \end{array}$ then you'll want to raise it by putting it into an \hbox along with a \raise command, as in
$\displaystyle M = \raise2ex\hbox{$\begin{array}{r|@{\hspace{9pt}}c@{ \hspace{12pt}}c@{\hspace{9pt}}|}\multicolumn{3}{r@ {\hspace{1pt}}}{\overbrace{}^{\textstyle m} \overbrace{}^{\textstyle n}} \\ p\,\{&A&B\\ q\,\{&C&D \end{array}$}$.