Displaymath

There are four environments that put LaTeX in math mode: math, displaymath, eqnarray, and equation. The math environment is for formulas that appear right in the text. The displaymath and equation environments are for formulas that appear on their own line; they differ only insofar as the latter prints an equation number. LaTeX will not break lines in displaymath or equation environments unless told to do so with a \\ command.

The displaymath environment can be entered by

  \begin{displaymath}
      math equation \\
      second line of math equation
  \end{displaymath}

Because displaymath may be used frequently to display relatively short equations, there are convenient alternative forms:

  \[ displayed math equation \]

or (the following does not seem to be well documented, but appears to work)

  $$ dispalyed math equation $$