Text Formatting ⇒ The & operator in piecewise functions

[sobrio35]

This code is producing the error message "Misplaced alignment tab character &". I've tried everything I can think of and no topics cover this that I can find. Ideas?

Code: Select all

\[
f(x) = 
\begin{cases}
1 & if 0 \leq x < \pi \\
0 & if \pi \leq x < 2 \pi
\end{cases}
\]

For now I really don't care about anything but compiling. The rest I can sort out later. Is there something easy I'm missing?

[Johannes_B]

Please always try to prepare a minimal working example. Simply adding a documentclass to your example shows, that there is nothing wrong with the code.

Code: Select all

\documentclass{article}
\usepackage{mathtools}
\begin{document}
\[
	f(x) =
	\begin{cases}
		1 & if 0 \leq x < \pi \\
		0 & \text{if } \pi \leq x < 2 \pi%please note the
%		extra text command 
	\end{cases}
\]
\end{document}

Please click on »open in writelatex« just above the code to test.

[Stefan Kottwitz]

I guess you forgot to load amsmath:

\usepackage{amsmath}

Johannes loaded mathtools, which automatically loads amsmath. That's why his example works fine. The older (non-amsmath) syntax of cases is different, that's why you would get this error.

Stefan

[Johannes_B]

When math is present, i always use mathtools. As Stefan already mentioned, it loads amsmath and also provides some fixes. If you need math, please read the docs of amsmath and mathtools. You will find some interessting things there.

Thanks @Stefan for pointing that out.