Displayed equations |

The LaTeX commands to format a formula as a
display differ from the commands to format an inline
formula only in the choice of the delimiters that identify
mathematics mode. In the following example, the pair `\[`

and `\]`

delimit display mathematics mode.

Here is a displayed \[\int\frac{d\theta} {1+\theta^2}= \tan^{-1}\theta+C\] equation.

An equivalent way to format the same displayed equation is to spell out the delimiters in words.

Here is a displayed \begin{displaymath}\int\frac {d\theta}{1+\theta^2} =\tan^{-1} \theta+ C\end{displaymath} equation.

A variant of the above is the following.

Here is a displayed \begin{equation}\int \frac{d\theta}{1+\theta^2}= \tan^{-1}\theta+C\end{equation} equation.

There is a difference between the `displaymath`

environment and the
`equation`

environment: the latter automatically typesets a formula
number.

The formatted output with no formula number is shown in the first figure.

The formatted output with a formula number is shown in the second figure.

**Warning** to former plain TeX users: in plain TeX,
double dollar signs
`$$`

are used to delimit display mathematics, but this convention
should not be used in LaTeX (although it will work
sometimes). The `fleqn`

document-class
option, for example,
operates by redefining `\[`

and `\]`

, but it pays no
attention to `$$`

.

A convenient feature of LaTeX is that it can automatically generate formula numbers. If you add or delete a numbered equation, you do not have to worry about revising the formula numbers: LaTeX does this chore for you.

What if you want to refer to a numbered equation by number? How
do you manage this if the equation number is automatically
generated? LaTeX has a simple `\label`

and `\ref`

mechanism for handling symbolic cross references. Here is an
example.

The formula \begin{equation} E=m c^2 \label{Einstein} \end{equation} has passed into popular culture, but the true significance of the mass-energy equation~(\ref{Einstein}) is~\ldots

(By the way, that tilde
`~`

is a *tie* or non-breaking space: it is good
typesetting style to keep a short label attached to its noun.)

If you use the amsmath package, then you
can type `\eqref`

instead of `\ref`

, and the
parentheses around the cited equation number will be supplied
automatically.

The Math 696 course pages were last modified April 5, 2005.

These pages are copyright © 1995-2005 by Harold P. Boas. All rights reserved.

Displayed equations |