- Given two sets A and B, the
intersection of these sets, denoted A ∩
B, is the set containing the elements that are in both
A and B. That is, A ∩ B =
{x : x ∈ A and x ∈
B}.
- Two sets A and B are
disjoint if they have no elements in common. That
is, if A ∩ B = ∅.
- Given two sets A and B, the union of
these sets, denoted A ∪ B, is the set containing
the elements that are either in A or in B (or in
both). That is, A ∪ B = {x : x
∈ A or x ∈ B}.
- Given two sets A and B, the relative
complement or difference of these sets, denoted
B −A, is the set of elements that are in
B but not in A. That is, B − A
= {x : x ∈ B and x /∈
A}.
- Given a universal set U and a set A, the
complement of the set A with respect to the set
U, denoted as AC or A,
is
the set U − A. That
is, A = {x ∈ U : x /∈
A}.
- Given two sets A and B, the symmetric
difference of these sets, denoted A ⊕ B, is
the set of elements that are in A or B but not
both. That is, A ⊕ B = (A ∪ B)
− (A ∩ B).
- Let A = {a,b,c,d,e,f}, B =
{a,c,e,f,g,h,i}, C = {b,c,d,f,g,h} and
U = {a,b,c,d,e,f,g,h,i,j}. Express each of the
following in roster notation.
(a) A ∪
B
(b) A ∩
B
(c) A ⊕ B
(d) A −
C
(e) C −
A
(f) C
(g) A − (B ∪
C)
(h) A ∪ (B ∩
C)
(i) (A ∪ B) ∩ (A ∪ C)
- Suppose U =
{1,2,3,4,5,6} and
B = {2,3,4}.
- What can you say about the set A if A ∪
B = {1,2,3,4,5}?
- What can you say about the set A if A ∩
B = {2,3}?
- What can you say about the set A if A ⊕
B = {1,2,4,5}?
- What can you day about the sets A and B if
A ⊕ B = ∅?
- Draw a general Venn diagram representing each of the
following:
- A ∩ B (b) A − B
(c) (A ∪ B) −
C
(d) A ∪ (B − C)