The Cartesian product A × A has 9 elements among which are found (–1, 0) and (0,1). Find the set A and the remaining elements of A × A.
n(A x A) = 9
n(A) c n(A) = 9 n(A) = 3
Also, n(A) = 3 A = (-1, 0, 1)
Hence, A = {-1, 0, 1}
Also, A x A = {-1, 0, 1} x {-1, 0, 1}
= {(-1, -1), (-1, 0), (-1, 1), (0, -1), (0, 0), (0, 1), (1, -1), (1, 0), (1, 1)}
Hence, the remaining elements of A x A are
(-1, -1), (-1, 1), (0, -1), (0, 0), (1, -1), (1, 0) and (1, 1).
Let A = {1, 2}, B = {1, 2, 3, 4}, C={5, 6} and D = {5, 6, 7, 8}. Verify that A x C is a proper subset of B x D.