Prove De Morgan's law by showing that AU B = A n B if A and B are sets. Prove De Morgan's law by showing that each side is a subset of the other side by considering xe AnB. Rank the options below. Hence, A UB is true. Using the definition of intersection, XE A AXE B. Using the definition of the complement of a set, XE AAX& B. Then, we can write (XE A) A (XEB). Therefore, we get xe AnB AUB Consider Xe An B. Applying De Morgan's law of proposition, we get (XE AVXe B)