# Splitting up an expression (that has braces)

I am trying to split up the longest set (the super long expression) here into multiple lines, I've looked at some other similar questions on this forum and tried a few different things but nothing seems to be working. I want it all aligned left like normal.

\documentclass{article}
\usepackage{amsmath}
\usepackage{graphicx}
\usepackage{amstext}
\usepackage{amssymb}
\begin{document}
\begin{enumerate}
\item Problem 1
$\varnothing \times B= \varnothing$ because $\varnothing \times B=\left \{ (a,b):a\in \varnothing , b\in B \right \}$ but there are no elements in $\varnothing$
\item $(A \times B)\times B$

From (a): $(A \times B)=\left \{ (1,c),(2,c),(3,c),(4,c),(1,a),(2,a),(3,a),(4,a) \right \}$
$(A \times B)\times B=$
\left \{ ((1,c),a),((2,c),a),((3,c),a),((4,c),a),((1,a),a),((2,a),a),((3,a),a),((4,a),a),((1,c),c),((2,c),c),((3,c),c),((4,c),c),((1,a),c),((2,a),c), ((3,a),c),((4,a),c) \right \}

\end{enumerate}
\end{document}

• amsmath loads amstext.
– cfr
Commented Apr 5, 2015 at 3:47
• If an answer addresses your question, you should mark it as such with a "Vee" symbol. Commented Apr 5, 2015 at 6:39
• It seems as if you are making your first steps with LaTeX. You may find it useful to consult the resources mentioned in this question: tex.stackexchange.com/questions/11/… Commented Apr 5, 2015 at 6:42

## 1 Answer

To break lines started with ${$ use "\right." and to start the next line use "\left." if ending that line with $}$. This is used in the example.

\documentclass{article}
\usepackage{amsmath}
\usepackage{graphicx}
\usepackage{amssymb}
\begin{document}
\begin{enumerate}
\item Problem 1
$\varnothing \times B= \varnothing$ because $\varnothing \times B=\left \{ (a,b):a\in \varnothing , b\in B \right \}$ but there are no elements in $\varnothing$
\item $(A \times B)\times B$

From (a): $(A \times B)=\left \{ (1,c),(2,c),(3,c),(4,c),(1,a),(2,a), (3,a),(4,a) \right \}$
\begin{align}
(A \times B)\times B &=
\left \{ ((1,c),a),((2,c),a),((3,c),a),((4,c),a),((1,a),a), \right.       \nonumber\\
& \hspace{5mm} \left. ((2,a),a), ((3,a),a),((4,a),a)
,((1,c),c),((2,c),c), \right. \nonumber\\
& \hspace{5mm} \left. ((3,c),c),((4,c),c),((1,a),c),((2,a),c), ((3,a),c),((4,a),c) \right \}
\end{align}

\end{enumerate}
\end{document}