How to typeset pmatrix Latex code in ipe text window?

When I enter

$
\begin{pmatrix}
1 & 2\\
3 & 4
\end{pmatrix}
$

into ipe text object, inside the small window that pops with saying to
enter Latex code, it gives a compile error.
-----------------------------------
  Misplaced alignment tab character &.
l.51 1 &
          2\\
I can't figure out why you would want to use a tab mark
here.
----------------------------------

Does IPE support pmatrix env. ? Do I need to add something in my
configuration? HOw to tell it to use \usepackage{amsmath}? If so,
I do not know how to.

IPE 7.2.2. on windows 7

thanks
--Nasser