# How do I type the infinity symbol in MacTex? [duplicate]

\item Obtain the one-to-one function $f_1$ and $f_2$ by cutting the graph of $f$ at
a certain point ($x_1$, $y_1$) so that domain of ($f_1$)=($-∞$ , $x_1$] and
domain ($f_2$)=[$x_1$,$+∞$)

## marked as duplicate by percusse, doncherry, egreg, Stefan Kottwitz♦Sep 18 '13 at 15:37

• Just a general tip: It's safter to use $$f_1$$ and $f_1$ than $f_1$ and $$f_1$$. For more information, see this question: tex.stackexchange.com/questions/503/why-is-preferable-to or read about it in l2tabu. – Sam Whited Sep 18 '13 at 15:11