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This question already has an answer here:

Overleaf is saying that both \unlhd and \trianglelefteq are undefined control commands, although \traingleleft works fine.

How else can I make normal subgroup symbol i.e. enter image description here

with an equality sign below.

marked as duplicate by egreg amsmath Jul 12 '15 at 9:56

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  • 1
    I don't know how overleaf actually works, but you might have to load the amssymb package. – Bernard Jul 12 '15 at 1:04
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You need the amssymb package:

\documentclass{article}
\usepackage{amssymb}

\begin{document}
$H \unlhd G$
\end{document}

output

Or even without the package you could say:

\documentclass{article}

\DeclareSymbolFont{AMSa}{U}{msa}{m}{n}
\DeclareMathSymbol{\Bhaskarunlhd}{\mathrel}{AMSa}{"45}

\begin{document}
$H \Bhaskarunlhd G$
\end{document}
  • @BhaskarVashishth, you're welcome, but note that the usual way of say thanks in this site is upvote any good answer (of any question) and accept the best answer (only one) to your own question. – Ruben Jul 12 '15 at 1:09
  • Yeah, I am aware of stack rules sir, but I was first trying it, I guess I am too dud with tex to actually use your help, or overleaf doesnot accept ams package. It didnt work. thanks anyways – Bhaskar Vashishth Jul 12 '15 at 1:12
  • Oh, ok. Overleaf seems to be a nasty little thing... – Ruben Jul 12 '15 at 1:13
  • @BhaskarVashishth, I added a package indipendent solution. – Ruben Jul 12 '15 at 1:40
  • Jjust copying it inside \(\) is giving many errors. I am not sure I am doing it right, acn you try it in a blank page in overleaf.com and see how can I make it work. If you are not busy, thanks. Otherwise I will just use the one without equal sign, not a problem – Bhaskar Vashishth Jul 12 '15 at 1:47

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