LaTeX sandbox is too short

Ok, I entered the same text, and it worked for me

 

I'm confused...
The compiled (?) formula shows up in your reply but not in my post. A clue, please?

 

I have no clue. Have you tried re-typing it? Or try in another browser?

Tex always has worked for me, so I tried in your thread to eliminate any site changes as the cause.

 

Just copied and pasted.

 

Good. I suspect there was a non-printable character embedded in your original post, that was not copied during the copy and paste operation.

 

Found it!
I had cut and pasted an example into my original post which delimited the TEX argument with "plain" and "/plain", ostensibly to show the raw Tex format in the article I got the sample from without compiling the argument.
Anyway, I just now edited out the "plain" and the "/plain", and everything works.
Thanks for the help.

 

Yes; thank you.