union3

A union empty set eq A

W3C sample	WIRIS
	$A φ A$

<math xmlns="http://www.w3.org/1998/Math/MathML">
  <apply>
    <eq/>
    <apply>
      <union/>
      <ci>A</ci>
      <cn>&#x003C6;</cn>
    </apply>
    <ci>A</ci>
  </apply>
</math>

Author: Design Science, Inc. (E. Cannon, E. Tabacman, R.Miner)