Hi DS,
I just put
\triangle
\(\triangle\)
Complex's triangle looks a little different from mine, I am going to look at the code.
\(\mbox{triangle from ribbon}\;\;\;\Delta \\~\\ \mbox{The command for that is \Delta}\)
What do you want to label ?
Maybe you should be using GeoGebra ?
I don't think you can. I think it just represents triangle.
Ex.
\(\Delta ABC\)