# How to make brackets bigger?

I have the following expression here.

$$\{\|\frac{f_i(x_i+h)-f_i(x-k)}{h}\|\}$$


I want to make the outer most brackets and the modulus sign to be bigger.

I have tried

$$\Bigg{\Bigg|\frac{f_i(x_i+h)-f_i(x-k)}{h}\Bigg|\Bigg}$$


but this doe not seem to work.

What can I do?

• \Biggl\{\biggl|...\biggr|\Biggr\}. And don’t use ! – GuM Aug 10 '16 at 9:32
• They work fine, but the braces are \{ ... \} not {...}, also consider using \Biggl ... \Biggr in order to get the correct classes. – daleif Aug 10 '16 at 9:32
• – GuM Aug 10 '16 at 9:43

\Bigg{ and \Bigg} are errors; it should be \Bigg\{ and \Bigg\}, respectively.
Actually, there's no need to \Bigg (pun intended) -- \bigg is the correct size for the fractional term at hand. Thus, you should enter the displayed equation as follows:
$\biggl\{\biggl| \frac{f_i(x_i+h)-f_i(x-k)}{h} \biggr|\biggr\}$

Note that I use \biggl and \biggr instead of just \bigg for the "fence symbols". For the present equation this makes no difference in appearance. However, there would be a major difference if the fractional expression were preceded by a unary minus (or plus) symbol.
You can try \right\{ and \left\{. These commands adjust the size of the braces to their contents.
• \{. Your answer has the same omission as the OP. – Willie Wong Aug 10 '16 at 14:49