# 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? • If I remember correctly, \triangledown requires the amssymb package, so let’s begin by eliminating the obvious: are you loading that package? Ah, and Welcome to TeX.SX! I didn’t notice it before. – GuM Mar 28 '16 at 0:29 ## 1 Answer If the error message is: ! Undefined control sequence. <recently read> \triangledown l.3$\triangledown
$?  then a package is missing, which provides the symbol. For example, package amssymb provides the symbol: \documentclass{article} \usepackage{amssymb} \begin{document}$\triangledown$\end{document}  If you want to have the nabla symbol, then this symbol is available without additional packages: \documentclass{article} \begin{document}$\nabla\$
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• I was actually looking for the nabla symbol but didn't know they are different. Thank you so much! – Penemonie Mar 28 '16 at 1:21