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Latest news 2019-11-04: The giveaway of two signed copies of “Quack, quack, quack. Give my hat back!” has closed and the winning entrants have been selected. Thank you to everyone who took part.


9.2 Displayed Mathematics

One-line unnumbered displayed mathematics can be created using:

\[<maths>\]

where <maths> is the mathematics to be displayed.

Example:

A linear function is a function of the form
\[ y = mx + c \]

Output:

Image showing typeset output (click here for a more detailed description).

Don't use the displaymath environment or $$...$$ [15]. Use \[ and \] with the amsmath package.

The equation environment provides something similar to \[ \], except that the equation is numbered. Modifying the above example:

A linear function is a function of the form
\begin{equation}
y = mx + c
\end{equation}

results in the following output:

As before but the equation now has a number in
brackets on the right.

Normal text can be inserted into the equation using

\text{<text>}

which is provided by the amsmath package.

Example:

\[ x = 2 \text{ and } y = -1 \]

results in the following output:

x equals 2 and y equals minus 1 (the word 'and' is in normal text font)

[Re-using an equation]Recall from §5.5. Cross-Referencing that we can cross-reference most things that LaTeX automatically numbers using \ref and \label. Equations can be cross-referenced in the same way:

Equation~\ref{eqn:linear} is a linear function.
\begin{equation}
\label{eqn:linear}
f(x) = mx + c
\end{equation}

Image showing typeset output (click here for a more detailed description).

Equation numbers are usually given in parentheses, which can be done using:

Equation~(\ref{eqn:linear})

The amsmath package provides a convenient short cut:

\eqref{<label>}

So the above can be written as:

Equation~\eqref{eqn:linear}

Equation (9.2)

Note:

Both the equation environment and \[...\] are only designed for one line of maths. Therefore you must not have any line breaks or paragraph breaks within them. The following will cause an error:

\begin{equation}

f(x) = mx + c

\end{equation}
Either remove the blank lines or comment them out:
\begin{equation}
%

f(x) = mx + c
%

\end{equation}


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