A union empty set eq A
<math xmlns="http://www.w3.org/1998/Math/MathML"> <apply> <csymbol cd="relation1">eq</csymbol> <apply> <csymbol cd="set1">union</csymbol> <ci>A</ci> <ci>φ</ci> </apply> <ci>A</ci> </apply> </math>
Author: Design Science, Inc. (E. Cannon, E. Tabacman, R.Miner)