# Breaking a long math expression

I am trying to type long expression by using parenthesis inserting some sentences, as an example I have a expression like product of

\documentclass{12 pt}{article}
\begin{document}
\begin{multline}
(product of (A\times_{c} B) by C)\times_{c} D) by E.
\end{multline}
\end{document}


I am using multline environment but I have problem with breaking into different lines. Is there any easy way to break the lines?

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Welcome to TeX.sx! Please add a minimal working example (MWE) that illustrates your problem. It will be much easier for us to reproduce your situation and find out what the issue is when we see compilable code, starting with \documentclass{...} and ending with \end{document}. –  Torbjørn T. Apr 23 '13 at 5:43
Without knowing anything about what you're doing, I predict that the problem is that your parentheses are paired using \left( and \right). These cannot be broken across lines; if you need both large parentheses and line breaks, you will need to select their sizes manually. See this answer, for example, for a list of sizes. –  Ryan Reich Apr 23 '13 at 5:49
Thank you – Torbjørn T. I have a expression like product of (product of (A\times_{c} B) by C)\times_{c} D) by E. –  Rajesh Apr 23 '13 at 5:54
TeX code would be preferable. Read the link that @TorbjørnT provided. –  Ryan Reich Apr 23 '13 at 6:32
@Jubobs That works but only gives brackets of matching sizes if each ... expression has the same height/depth. –  Andrew Swann Apr 23 '13 at 10:46

The mathmode document by Herbert Voß provides an example how to use the multiline environment on page 51. The easy way to break lines is adding \\ at the position where you want the line break to occur.

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We're looking for long answers that provide some explanation and context. Don't just give a one-line answer; explain why your answer is right, ideally with citations. Answers that don't include explanations may be removed.

It is quite hard to answer your question as the example code supplied doesn't give many clues. However [12pt] needs to be in square brackets, and you need to mark up text in math specially (I'm using \text from the amsmath package). Then line breaks can be marked with \\

\documentclass[12pt]{article}
\usepackage{amsmath}
\begin{document}
\begin{multline}
(\text{product of} \\
(A\times_{c} B) \text{ by } C \\
)\times_{c} D)\text{ by } E \text{.}.
\end{multline}
\end{document}

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Thank you all for nice answer. –  Rajesh Apr 23 '13 at 12:58