Environments

There are quite a lot of useful environments.

Align

\usepackage{amsmath}

\begin{align*}
    2 + 2 &= 4 \\
    4 &= 2 + 2
\end{align*}

The & is the alignment character.

\[ \begin{align} 2 + 2 &= 4 \\ 4 &= 2 + 2 \end{align} \]

Array

This environment needs to be nested within a math environment, such as $$.

\begin{array}{ccc}
    2 &= &2 \\
    4 &= &4
\end{array}

The & divides the equation like slices.
The \(\{ccc\}\) means 3 characters which are centered.
Alternatively, we can write \(r\) for right and \(l\) for left.

\[ \begin{array}{ccc} 2 &= &2 \\ 4 &= &4 \end{array} \]

Center

It is used to center objects.

\begin{center}
\end{center}

Alternatively:

\centering