# Hypertext Help with LaTeX
\lefteqn

     \lefteqn{eqn}

prints `eqn` in display math style, but pretends that it has zero width. It is typicaly used within an `Eqnarray` environment for displaying long equations that require multiple lines.

A typical use might be

      \begin{eqnarray}
      \lefteqn{\int_0^\infty some expression =} \\
      & & some terms \\
      & & \mbox{} + more terms
      \end{eqnarray}

Note that the empty `\mbox{}` is so LaTeX knows that the following `+` is a binary operator, and is not attached to the first of the "more terms" as a unary operator.

Related topics

- Environments
- Array Environment
- Eqnarray Environment
- Equation Environment
- Displaymath Environment
- Math Formulas

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