® Cartesian product A × B of two sets A and B is given by

® Cartesian product A × B of two sets A and B is given by A × B = {( a , b ): a ∈ A, b ∈ B} In particular R × R = {( x , y ): x , y ∈ R } and R × R × R = ( x , y , z ): x , y , z ∈ R } ® If ( a , b ) = ( x , y ), then a = x and b = y. ® If n (A) = p and n (B) = q , then n (A × B) = pq .