Elements here are in set A, but not in set B ( A\B )
B
Elements here are in set B, but not in set A ( B\A )
Elements here are in both sets A and B ( A∩B )
Discuss and discover
(i) Copy the diagram for two given sets A and B. (a) Shade in A∪B . (b) Copy the diagram again, and shade in B∪A . (c) Are the shaded areas the same?
(d) Does the order of the sets matter when asked to fi nd the union of two sets?
(e) Is A∪B = B∪A ?
(ii) (a) Using the same diagram provided, investigate if A∩B = B∩A . (b) Do you think the order of two sets matters when asked to fi nd the intersection of two sets?
(iii) (a) Copy diagram provided, and shade in A\B . (b) Copy the diagram again, and shade in B\A . (c) Are the shaded areas the same? (d) Does the order of the sets matter when asked to fi nd the difference of two sets? (e) Is A\B = B\A ?
Commutative property The commutative property applies to all sets.
The commutative property states that the union of two sets is the same no matter what the order is in the equation. It also states that the intersection of two sets is the same no matter what the order is in the equation.
A∪B = B∪A and A∩B = B∩A
Note: Since A\B ≠ B\A we can state that the diff erence between two sets is not commutative. Therefore, the order of the sets does matter in the notation.