LaTeX Questions Answered

# 47 How do I make brackets around an expression bigger?

For our purposes, “brackets” refers to (parentheses), [square brackets], {curly brackets}, and 〈angle brackets〉, as well as |vertical bars or pipes| and ||double pipes||.

There may be times when you want your brackets to appear larger than the standard size, such as when you have brackets around a fraction. Luckily, it is very easy to make your brackets match the size of whatever they are trying to contain.

Use the commands `\left`

and `\right`

to create brackets that will resize themselves to match what they surround.

For example, say you want to put parentheses around a fraction. If you use regular parentheses, the expression looks like this:^{[1]}

[latex](\dfrac{3x+4}{2})[/latex]

As you can see, the expression isn’t properly contained by the parentheses. Here’s what it looks like when you write `\left(`

and `\right)`

around the expression:

[latex]\left(\dfrac{3x+4}{2}\right)[/latex]

Just like that, the parentheses have resized themselves to fit around the fraction.

These dynamic brackets are not always necessary: if your bracketed expression is just a few alphanumeric characters, regular brackets will probably work just fine. But these commands are very useful for when you have a larger expression that you’d like to contain in brackets.

See the following table to learn how to write all the different kinds of brackets.

Bracket | LaTeX Markup | Rendered |
---|---|---|

(Parentheses) | `(a-b)` |
[latex](a-b)[/latex] |

[Square brackets] | `[a-b]` |
[latex][a-b][/latex] |

{Curly brackets} | `\{a-b\}` |
[latex]\{a-b\}[/latex] |

〈Angle brackets〉 | `\langle a-b \rangle` |
[latex]\langle a-b \rangle[/latex] |

|Vertical bars or pipes| | `|a-b|` |
[latex]|a-b|[/latex] |

||Double pipes|| | `\|a-b\|` |
[latex]\|a-b\|[/latex] |

Now let’s see how to write each type of dynamic bracket:

Bracket | LaTeX Markup | Rendered |
---|---|---|

(Parentheses) | `\left(\dfrac{a}{b}\right)` |
[latex]\left(\dfrac{a}{b}\right)[/latex] |

[Square brackets] | `\left[\dfrac{a}{b}\right]` |
[latex]\left[\dfrac{a}{b}\right][/latex] |

{Curly brackets} | `\left\{\dfrac{a}{b}\right\}` |
[latex]\left\{\dfrac{a}{b}\right\}[/latex] |

〈Angle brackets〉 | `\left\langle\dfrac{a}{b}\right\rangle` |
[latex]\left\langle\dfrac{a}{b}\right\rangle[/latex] |

|Vertical bars or pipes| | `\left|\dfrac{a}{b}\right|` |
[latex]\left|\dfrac{a}{b}\right|[/latex] |

||Double pipes|| | `\left\|\dfrac{a}{b}\right\|` |
[latex]\left\|\dfrac{a}{b}\right\|[/latex] |

For those types of brackets that require a command of their own and can’t just be written as is — such as the curly brackets, which must be written as `\{x\}`

— the syntax of the `\left`

and `\right`

commands can start to look a little confusing, especially when combined with other commands.

Just remember that the syntax goes `\left`

, *symbol for the opening bracket*, `\right`

, *symbol for the closing bracket*.

- You can right-click this expression and go to
**Math Settings > Math Renderer > Plain Source**and then back to**Common HTML**to switch between seeing the original LaTeX markup and the expression in display form. ↵