How can I write a piecewise function in LaTeX?

[TheBigBadBen]

I was trying to type a piecewise function, and then this happened:

$$
f(x)=\left{ \begin{array}{ccc}
1 & x \in \mathbb{Q} \\
0 & x \notin \mathbb{Q}
\end{array} \right
$$

What's going on, and how do I fix it?

 

[Jameson]

Hi TheBigBadBen, :)

There are two small things to fix and it works just fine. The first is when you want to add brackets {} using Mathjax you need to add another slash before it. So it should read "\left \{". The other thing is at the end of "\right" you need to add a period. If you do those two things this is what renders.

$$
f(x)=\left\{ \begin{array}{ll}
1 & x \in \mathbb{Q} \\
0 & x \notin \mathbb{Q}
\end{array} \right.$$

 

[MarkFL]

Another approach:

Try the code:

f(x)=\begin{cases}1 & x\in\mathbb{Q}\\ 0 & x\notin\mathbb{Q} \\ \end{cases}

to get:

$$f(x)=\begin{cases}1 & x\in\mathbb{Q}\\ 0 & x\notin\mathbb{Q} \\ \end{cases}$$