Cases

This is not hard to find, but I still seem to forget it every now and then ;)

The cases environment is useful to display a function that has a different value in several cases:

$$U[n]= \begin{cases} 0& \text{if } n<0\\ 1& \text{if } n\geq 0\\ \end{cases}$$

This is made with the following source:

\[
U[n]=
  \begin{cases}
	0& \text{if } n<0\\
	1& \text{if } n\geq 0\\
  \end{cases}
\]