## displaying an array

from a forum post by carl brannen i get the following code for an array: $\left(\begin{array}{cc}0.5&+0.5\\-0.5&0.5\end{array}\right)^2 =\left(\begin{array}{cc}0.5&+0.5\\-0.5&0.5\end{array}\right)$

let’s figure out how to get the array i want. do it here, of course, where i’ve got his code. $\left(\begin{array}{cc}\Sigma&0\\0&0\end{array}\right)$

there’s a bug. i want backslash backslash 0&0

but i have to type backslash backslash backslash 00&0

because the translator seems to eat the first “backslash 0”.  every time i edit the post! argh!

clearly i need to use UC O instead of zero.

$\left(\begin{array}{cc}\Sigma&O\\O&O\end{array}\right)$