Math & Science ⇒ equations and cases

[phillyj]

Hi all, I'm new here and new to latex. I am using latex to type up my probability notes and ran in a problem. I tried google but not much help especially considering I'm not sure what to call my problem.

I have an equation [P(A)= summation = cases]

The problem is that they come out too long. I wanted to stack the 1st part [P(A)] above the 2nd two. I tried multiline but I have trouble with it. How do I approach this? Below is the raw code I used:

Code: Select all

\begin{equation}
	 P(A_{1} \cup A_{2}\ \cup A_{3} \cup~\ldots)= \sum_{i=1}^{\infty}P(A)_{i}=\begin{cases}
			A_{1},A_{2},A_{3}~\ldots 	&\text{are countable numbers;}\\
			A_{i} \cap A_{j} = \emptyset	&\text{$i \ne j$}	
	\end{cases}
\end{equation}

Thanks

[localghost]

I'm not sure if this is what you want. But it always can serve as a first approach.

Code: Select all

\documentclass[11pt,a4paper]{article}
\usepackage[T1]{fontenc}
\usepackage[latin1]{inputenc}
\usepackage{amsmath}

\begin{document}
  \begin{equation}
    \begin{aligned}
      P(A_{1}\cup A_{2}\cup A_{3}\cup\ \ldots)&= \\
      \sum\nolimits_{i=1}^{\infty}P(A)_{i}&=
    \end{aligned}
    \begin{cases}
      A_{1},A_{2},A_{3},\ \ldots & \text{are countable numbers;}\\
      A_{i} \cap A_{j} = \emptyset & \text{$i \ne j$}   
    \end{cases}
  \end{equation}
\end{document}

Best regards and welcome to the board
Thorsten¹