# How do I define a piecewise function in latex?

I just saw this question but it doesn't answer mine. How do I define a function something like

f(x) = { bla bla if x<0 bla bla if x>0

The above question doesn't answer how to write f(x) before the bracket

• If you want f(x)= before the bracket, then just write f(x)= before the \begin{cases} (and after the \$ or $) Commented Apr 21, 2017 at 17:38 ## 2 Answers LaTeX is very flexible. Although it is not WYSIWYG you can write it in a very logical way. So if you want to have to have f(x) precede your cases, just write it that way. Here with the example of the linked question. \documentclass{article} \usepackage{amsmath} \begin{document} \[ f(x) = \begin{cases} 0 & x\leq 0 \\ \frac{100-x}{100} & 0\leq x\leq 100 \\ 0 & 100\leq x \end{cases}$
\end{document}

• @Zarko C&P from the linked post in OP. I should have looked at it ;) But I'm too lazy to change for now. Commented Apr 21, 2017 at 17:46
• Say, instead of a left curly brace is it possible to define a left bracket i.e, "[" for this command Commented Jan 30 at 13:44
• @Cristofer That's not built into LaTeX. While you can cheat using \left[\begin{array}{ll}…\end{array}\right. it's better to ask a new question with your specific requirements. Commented Jan 31 at 9:41

TeX is very flexible. Although it is not WYSIWYG you can write it in a very logical way. So if you want to have to have f(x) precede your cases, just write it that way.

$$f(x) = \cases{ 0 & x\le 0 \cr 100-x\over 100 & 0\le x\le 100 \cr 0 & 100\le x }$$
\bye

• Maybe someone didn't understand the joke :-) Commented Jun 9, 2020 at 17:26