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Possible Duplicate:
How to look up a symbol?

I'd like to write the unity element 1 in LaTeX. I have tried these methods: 

$\mathbbm{1}$ \\
$\mathbb{1}$\\
$\mathbbss{1}$\\
$\mathbbtt{1}$\\
$\mathds{1}$\

but I receive the integer 1. I think that I'm missing a suitable package. How to solve this problem?

David Carlisle
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Chouria Ali
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  • Does this help?: http://www.douglas.stebila.ca/blog/archives/2004/06/27/latex-blackboard-bold-1/ – Jellby Jul 05 '12 at 10:59
  • If you load the package bbold, you can type \mathbb{1} (in math-mode, of course) to get what you want. The "standard" blackboard bold glyphs are available only for uppercase letters -- hence the need to load an extra package. – Mico Jul 05 '12 at 10:59
  • @Mico I believe you have answered the question. I recommend you post your comment as an answer. – azetina Jul 05 '12 at 14:34
  • @azetina: done! – Mico Jul 05 '12 at 15:25

1 Answers1

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The "standard" blackboard bold math font contains only uppercase latin-alphabet letters. To get a blackboard bold "1" symbol, you need to load an additional LaTeX package.

For instance, the commands \mathbb{1} (load the bbold package) and \mathds{1} (load the dsfont package) will generate:

enter image description here

respectively.

Mico
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    It's been 12 years, but I just stumbled upon this post. I believe the second package is called \usepackage{dsfont} – infinitezero Mar 02 '18 at 15:37
  • @infinitezero - You're absolutely right! Many thanks for pointing it out. I'll fix this issue right away. – Mico Mar 02 '18 at 15:44