Importing LaTeX from Lyx?

I've tried using Lyx to typeset a multiline formula; viewing a .pdf of the output within Lyx is absolutely fine - everything looks as desired without any problem.

However, when I paste the LaTeX code into the board here (with the appropriate math tags), I receive a LaTeX syntax error. Why should this be?

Here's the code I tried to paste:

\begin{eqnarray*} x & = & \frac{4}{100}e^{\frac{-1}{100}t}\sin(12t)\\

\: & = & {\rm Re}\left(ce^{\alpha+i\beta}\right)\\

\: & = & {\rm Re}\left(ce^{\alpha}e^{i\beta}\right)\\

\: & = & {\rm Re}\left(ce^{\alpha}\left[\cos\beta+i\sin\beta\right]\right)\\

\: & = & ce^{\alpha}\cos\beta\\

\frac{4}{100}e^{\frac{-1}{100}t}\sin(12t) & = & ce^{\alpha}\sin\left(\beta+\frac{\pi}{2}\right)\en d{eqnarray*}