Definition A×B={(a,b)∣a∈A∧b∈B} where A,B are sets The set of all ordered pairs (a,b) where a∈A∧b∈B Facts A×∅=∅×A=∅ A×(B∩C)=(A×B)∩(A×C) A×(B∪C)=(A×B)∪(A×C) A×(B−C)=(A×B)−(A×C)