A = B implies that A union C is equal to B union C
<math xmlns="http://www.w3.org/1998/Math/MathML"> <apply> <implies/> <apply> <eq/> <ci>A</ci> <ci>B</ci> </apply> <apply> <eq/> <apply> <union/> <ci>A</ci> <ci>C</ci> </apply> <apply> <union/> <ci>B</ci> <ci>C</ci> </apply> </apply> </apply> </math>
Author: Design Science, Inc. (E. Cannon, E. Tabacman, R.Miner)