How to break long equations with LyX

[list_email at icloud.com]

I have tried mightily to get LyX to break long equations. I’ve studied multiple pages at stackexchange, both LaTeX and LyX, and can’t seem to get anything to work.

I have had luck in the past with the second large block of code at this page:

https://stackoverflow.com/questions/2904807/lyx-breaking-long-formula-lines

but today I have some problems with it.

First, it doesn’t work if the \text command appears inside my own LaTeX code that appears between \begin{dmath} and \end{dmath} or if I try to use the trick twice in the same document. (That’s a tentative analysis of the problem.) Specifically, LyX runs at 100% CPU eventually gives me a chance to abort and then follows up with this additional message: "The external program pdflatex finished with an error. It is recommended you fix the cause of the external program's error (check the logs)."

Plus, I now want to to apply the line breaking to a line within an aligned environment (Insert -> Math -> Aligned Environment in the menu system.) This is causing things to look even worse, even though I added two “aligned” lines to the referenced code block. (If you look at the code you’ll see the obvious places to add the lines.)

How do LyX-ers handle this? Is there “LyX” solution to breaking long equations? I’m OK with some ad hoc solution for now, or some ERT if it works.

Thanks,
Jerry