I am trying to write some kind of blockmatrix
\[A_n=
\left(
\begin{array}{cc|cc}
&& 0 & 0 \\
& A_{n-2}&n-2&0 \\
\hline\\
0&-n+2&1&n-1 \\
0&0&-n+1&1
\end{array}
\right)
\]
How can I achieve that the entry in the upper left corner is written in center? Or rephrased: How is it possible two combine the columns (1,1)(1,2)(2,1) and (2,2)?
Best Answer
You're probably after the second of the following two instances (the first is yours):
Horizontal centering is achieved via
\multicolumn{2}{c}
, while vertical centering is obtained via\raisebox{.5\normalbaselineskip}
.\smash
removes any vertical distortion (from raising the boxed content), while the negative skip after\hrule
vertically aligns the vertical rules (top and bottom).