[Tex/LaTex] how to insert an upside-down triangle


I tried inserting an upside-down triangle with \triangledown but even when I put the two $ signs around it, I keep receiving an error.
Does anyone know how to insert such special characters?

Best Answer

If the error message is:

! Undefined control sequence.
<recently read> \triangledown

l.3 $\triangledown

then a package is missing, which provides the symbol. For example, package amssymb provides the symbol:


\triangledown of amssymb

If you want to have the nabla symbol, then this symbol is available without additional packages: