Hello, I am trying to spread the ellipsis over many columns of a matrix... lyx shouts: The control sequence at the end of the top line of your error message was never \def'ed. If you have misspelled it (e.g., `\hobx'), type `I' and the correct spelling (e.g., `I\hbox'). Otherwise just continue, and I'll forget about whatever was undefined.
Is there a specific miktex (mpm.exe) package I need to see installed? Rds,