## Precalculus (6th Edition)

$R \cup \emptyset = R$
RECALL: (1) $\emptyset$ is the empty set (2) The symbol $\cup$ represents union of sets which lists down in a set the combined elements of the given sets. Since the empty set has no elements., then its union with any other set will be the other set itself. Thus, $R \cup \emptyset = R$