# How to use symbols such as \delta and \lambda

I'm trying to use symbols such as \lambda and \delta but for some reason it's not compiling. I've reproduced the problem in the following code:

\documentclass[12pt,a4paper,oneside]{article}

\begin{document}

\begin{center}

M = < X,Y,S,ta, \delta int, \delta ext, \lambda >

\end{center}

\end{document}


I'm getting the following errors:

Missing $inserted M = < X,Y,S,ta, \delta Missing$ inserted I've inserted a begin-math/end-math symbol since I think

Missing } inserted I've inserted something that you may have forgotten.
Extra }, or forgotten \endgroup


Despite these errors, I can still view it in a PDF and it looks like the following:

So, just to clarify what I actually want:

1. To compile without the errors i.e. how do you make use of symbols like \delta etc?

2. How do I actually make it display like the following :

3. As depicted above, I want int and ext to be subscripts to the \delta symbols

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First, you need to surround the relevant line with $ symbols. Second, use underscores to create subscripts (and, for multiple-character subscripts, use curly braces as well). Thus, $M = < X,Y,S,ta, \delta_{int}, \delta_{ext}, \lambda >\$ –  Andrew Uzzell Nov 5 '12 at 11:18
@AndrewUzzell < and > in this case are definitely wrong. –  egreg Nov 5 '12 at 11:25
@egreg You're absolutely right. Also, when I posted my comment, I hadn't realized that the question was asking for how to typeset a displayed equation. In sum, egreg's answer is much more useful than my comment. –  Andrew Uzzell Nov 5 '12 at 11:29
This question shouldn't be downvoted. It may be a basic problem, but the question itself is very clear. Please don't downvote without explaining your reason to do so. –  Jake Nov 5 '12 at 11:31
In addition to Jake's comment, unlike SO in general, beginner questions are more than welcome in TeX.SE so please don't downvote if the question seems trivial to you. The question has a valid MWE and a good formulation. –  percusse Nov 5 '12 at 11:34

You want a centered formula; so the correct way to do it is

\documentclass[12pt,a4paper,oneside]{article}

\begin{document}

$M = \langle X, Y, S, ta, \delta_{\mathrm{int}}, \delta_{\mathrm{ext}}, \lambda \rangle$

\end{document}


This is covered in any basic LaTeX manual, for example The not so short introduction to LaTeX

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Thanks. But what is the reason behind not using \begin{center}? and why was my question down voted, so I know what I did wrong? –  D.Singh Nov 5 '12 at 11:19
center is for centering text, not math. I don't know why the question was downvoted; however, it's very basic and reading an introduction to LaTeX would really help to understand its principles, which are rather different from common word processors. –  egreg Nov 5 '12 at 11:22
Oh okay. Thanks for the reference as well, will use it for any further issues before I ask on here again.. –  D.Singh Nov 5 '12 at 11:23
@Jatt My comment was not meant for restraining you from asking here even basic level questions. Everybody is welcome, in my opinion. The fact is that LaTeX needs a different attitude than word processors; its main principle is separation of structure from visual appearance, so math is different from text and this reflects in how they're input. –  egreg Nov 5 '12 at 11:43
Thanks for that. I will look further into it. Ps. Your comment did not at all restrain me from asking questions in the future. I agree with you, I should've researched more before asking for help. –  D.Singh Nov 5 '12 at 11:51