## Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

$A\cup B=\{1,2,3,4,5,6,7,8,9\}$
$A\cup B$ is the set of elements that are either in A, or in B, or in both. Hence, here we have $A\cup B=\{1,2,3,4,5,6,7,8,9\}$