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

  \lefteqn{\int_0^\infty some expression =} \\
  & & some terms \\
  & & \mbox{} + more terms
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 Return to LaTeX Table of Contents
Revised: Sheldon Green, 29 Jun 1995.