Mathematics for IGCSE & O level - Sets (Section 1 - No. 20)
Which of the following is true concerning the intersection of the set A and its complement, A'?
A ∩ A' = A
A ∩ A' = A'
A ∩ A' = U (Universal set)
A ∩ A' = {} (Empty set)
Explication
The set A' contains everything not in A, so their intersection is nothing, hence empty.