# How can I align array elements to the left in an equation?

I have an equation that goes as follows:

\left\{ {\begin{array}{*{20}{c}}
{u{'_0} = {u_0} + u_1^Tt + {\textstyle{1 \over 2}}{t^T}{U_2}t}\\
{u{'_1} = {u_1} + {U_2}t}\\
{U{'_2} = {U_2}}
\end{array}} \right.


I want to have the elements of the array aligned to the left, as it is not very elegant as it is now. Still i dont want the whole equation to be on the left of the page, but on the centre, as usual. How can I achieve this?

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Why don't use just use the cases environment? Then you don't have to add the brace or the array construction. BTW: Any particular reason for using the \over construction and not just (in this case) \tfrac{...}{...} – daleif Jun 13 '13 at 7:58
Provide a minimal example please, inserting your code into a document does not compile... Anyway I suggest to use the cases environment – Red Jun 13 '13 at 8:01
@daleif Well the main reason of doing it like this is that I am pretty new to LaTeX and I use MathType. I just write my equation and copy paste it to the .tex file... If you have other idea of how to aproach the problem please feel free to comment it! Latex is such a huge world for a starter... – Ander Biguri Jun 13 '13 at 8:05
@Red ... The screenshot is from the result pdf... – Ander Biguri Jun 13 '13 at 8:06
@daleif the over solution is just to have a smaller 1/2, it felt nice that way. – Ander Biguri Jun 13 '13 at 8:08

(With at least a few improvements):

\documentclass{article}
\begin{document}

$%$$\left\{ \begin{array}{l} u'_0 = {u_0} + u_1^Tt + {\textstyle{1 \over 2}}{t^T}{U_2}t\\ {u'_1} = {u_1} + {U_2}t\\ {U'_2} = {U_2} \end{array} \right. %$$$

\end{document}


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your code does not compile in my document...PD: sorry it does. corrupted aux file – Ander Biguri Jun 13 '13 at 8:10
Then please post a full minimal example, so we can see what you are doing. – daleif Jun 13 '13 at 8:12
@daleif it does compile, my faul. corrupted aux file. This answer is good. – Ander Biguri Jun 13 '13 at 8:13

Better solution if you are a new user

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{equation*}
\begin{cases}
u'_0 = {u_0} + u_1^Tt + \tfrac{1}{2}{t^T}{U_2}t
\\
{u'_1} = {u_1} + {U_2}t
\\
{U'_2} = {U_2}
\end{cases}
\end{equation*}
\end{document}

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Thanks, ill take a look. Anyway the other solution is pretty nice and easy to understand also :D – Ander Biguri Jun 13 '13 at 8:15
ops, there was a typo, cases does not take an argument, it is a two column array with a build in brace on the left. The mathtools package provide extra cases-like constructions – daleif Jun 13 '13 at 9:07

I feel duty bound to give some advice on a very important point made by Ander Biguri when he explained in a comment to his question that his original code came from MathType. This is a significant point that should be pursued further. I myself have 260 pages of a Physics text that I was writing before I returned to university last year and was turned on to using TeX and then later to LaTeX.

MathType does not produce very good translations of its equations into LaTeX. More often than not significant editing is required. I would only suggest bothering to do this if you already, like me, have a lot of MathType work that needs translating. Personally, I do not do any new work with MathType. As a maths student and teacher, I now do all my assignments, articles, presentations, whatever with LaTeX. It's well worth persevering with LaTeX.

If you are starting out learning LaTeX and will continue to do so, you will find that it can solve virtually any maths typography problem out there. There is a good unofficial manual online at LaTeX Reference Manual and you can download a pdf version. Starting with a document like this you can discover all the usual LaTeX commands and when you get stuck ask a question here.

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