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LaTeX provides commands for making overlines or underlines, or putting braces over or under some material.

`\underline{`

`text`}Underline

`text`. Works inside math mode, and outside. The line is always completely below the text, taking account of descenders, so in`\(\underline{y}\)`

the line is lower than in`\(\underline{x}\)`

. This command is fragile (see \protect).Note that the package

`ulem`does text mode underlining and allows line breaking as well as a number of other features. See the documentation on CTAN. See also \hrulefill & \dotfill for producing a line, for such things as a signature.`\overline{`

`text`}Put a horizontal line over

`text`. Works inside math mode, and outside. For example,`\overline{x+y}`

. Note that this differs from the command`\bar`

(see Math accents).`\underbrace{`

`math`}Put a brace under

`math`. For example, this`(1-\underbrace{1/2)+(1/2}-1/3)`

emphasizes the telescoping part. Attach text to the brace by using subscript,`_`

, or superscript,`^`

, as here.\begin{displaymath} 1+1/2+\underbrace{1/3+1/4}_{>1/2}+ \underbrace{1/5+1/6+1/7+1/8}_{>1/2}+\cdots \end{displaymath}

The superscript appears on top of the expression, and so can look unconnected to the underbrace.

`\overbrace{`

`math`}Put a brace over

`math`, as with`\overbrace{x+x+\cdots+x}^{\mbox{\(k\) times}}`

. See also`\underbrace`

.

The package `mathtools` adds an over- and underbrace, as well as
some improvements on the braces. See the documentation on CTAN.