Take the 2-minute tour ×  How can I denote a limit in LaTeX,
such as $f(n) \rightarrow_{n \rightarrow \infty} 0$ ?  And when
I have a fraction and so on and I want to use an absolute value
$| \frac{x}{y}|$, how can I make the $|$ signs much bigger
(similarly to \left( and \right)) ?  share|improve this question
5 Answers 5  up vote 8 down vote accepted  For the first
question, you can typeset limits using the \lim command:   \[
\lim_{x\to\infty}\frac{1}{x} \]  For the second question, the
\left, \middle and \right commands can be used to achieve
vertical extension of some delimiters:  \[
\left\lvert\frac{1}{2} \right\rvert \]  To obtain fine control
on the size of extensible delimiters there are also the
following command groups (which in some circumstances, must
replace the \left \middle \right construct):  \bigl - \bigm -
\bigr \Bigl - \Bigm - \Bigr \biggl - \biggm - \biggr \Biggl -
\Biggm - \Biggr  These groups provide delimiters of increasing
sizes; the first column gives four sizes of opening symbols; t