Exercise for the break
Set theory/4 sets/Sketch complete diagram/Exercise
An abstract and
Exercises
Let
L
A
{\displaystyle {}LA}
denote the set of capital letters in the Latin alphabet,
G
A
{\displaystyle {}GA}
the set of capital letters in the Greek alphabet and
R
A
{\displaystyle {}RA}
the set of capital letters in the Russian alphabet. Determine the following sets.
G
A
∖
R
A
{\displaystyle {}GA\setminus RA}
.
(
L
A
∩
G
A
)
∪
(
L
A
∩
R
A
)
{\displaystyle {}{\left(LA\cap GA\right)}\cup {\left(LA\cap RA\right)}}
.
R
A
∖
(
G
A
∪
R
A
)
{\displaystyle {}RA\setminus {\left(GA\cup RA\right)}}
.
R
A
∖
(
G
A
∪
L
A
)
{\displaystyle {}RA\setminus {\left(GA\cup LA\right)}}
.
(
R
A
∖
G
A
)
∩
(
(
L
A
∪
G
A
)
∖
(
G
A
∩
R
A
)
)
{\displaystyle {}{\left(RA\setminus GA\right)}\cap {\left({\left(LA\cup GA\right)}\setminus {\left(GA\cap RA\right)}\right)}}
.
Determine for the sets
M
=
{
a
,
b
,
c
,
d
,
e
}
,
N
=
{
a
,
c
,
e
}
,
P
=
{
b
}
,
R
=
{
b
,
d
,
e
,
f
}
{\displaystyle M=\{a,b,c,d,e\},\,N=\{a,c,e\},\,P=\{b\},\,R=\{b,d,e,f\}}
the following sets.
M
∩
N
{\displaystyle {}M\cap N}
,
M
∩
N
∩
P
∩
R
{\displaystyle {}M\cap N\cap P\cap R}
,
M
∪
R
{\displaystyle {}M\cup R}
,
(
N
∪
P
)
∩
R
{\displaystyle {}{\left(N\cup P\right)}\cap R}
,
N
∖
R
{\displaystyle {}N\setminus R}
,
(
M
∪
P
)
∖
(
R
∖
N
)
{\displaystyle {}{\left(M\cup P\right)}\setminus {\left(R\setminus N\right)}}
,
(
(
P
∪
R
)
∩
N
)
∩
R
{\displaystyle {}{\left({\left(P\cup R\right)}\cap N\right)}\cap R}
,
(
R
∖
P
)
∩
(
M
∖
N
)
{\displaystyle {}{\left(R\setminus P\right)}\cap {\left(M\setminus N\right)}}
.
Sketch the following subsets of
R
2
{\displaystyle {}\mathbb {R} ^{2}}
.
{
(
x
,
y
)
∣
x
=
5
}
{\displaystyle {}{\left\{(x,y)\mid x=5\right\}}}
,
{
(
x
,
y
)
∣
x
≥
4
and
y
=
3
}
{\displaystyle {}{\left\{(x,y)\mid x\geq 4{\text{ and }}y=3\right\}}}
,
{
(
x
,
y
)
∣
y
2
≥
2
}
{\displaystyle {}{\left\{(x,y)\mid y^{2}\geq 2\right\}}}
,
{
(
x
,
y
)
∣
|
x
|
=
3
and
|
y
|
≤
2
}
{\displaystyle {}{\left\{(x,y)\mid \vert {x}\vert =3{\text{ and }}\vert {y}\vert \leq 2\right\}}}
,
{
(
x
,
y
)
∣
3
x
≥
y
and
5
x
≤
2
y
}
{\displaystyle {}{\left\{(x,y)\mid 3x\geq y{\text{ and }}5x\leq 2y\right\}}}
,
{
(
x
,
y
)
∣
x
y
=
0
}
{\displaystyle {}{\left\{(x,y)\mid xy=0\right\}}}
,
{
(
x
,
y
)
∣
x
y
=
1
}
{\displaystyle {}{\left\{(x,y)\mid xy=1\right\}}}
,
{
(
x
,
y
)
∣
x
y
≥
1
and
y
≥
x
3
}
{\displaystyle {}{\left\{(x,y)\mid xy\geq 1{\text{ and }}y\geq x^{3}\right\}}}
,
{
(
x
,
y
)
∣
0
=
0
}
{\displaystyle {}{\left\{(x,y)\mid 0=0\right\}}}
,
{
(
x
,
y
)
∣
0
=
1
}
{\displaystyle {}{\left\{(x,y)\mid 0=1\right\}}}
.
Let
A
,
B
{\displaystyle {}A,\,B}
and
C
{\displaystyle {}C}
denote sets. Prove the identity
A
∖
(
B
∩
C
)
=
(
A
∖
B
)
∪
(
A
∖
C
)
.
{\displaystyle {}A\setminus {\left(B\cap C\right)}={\left(A\setminus B\right)}\cup {\left(A\setminus C\right)}\,.}
Let
A
,
B
{\displaystyle {}A,B}
and
C
{\displaystyle {}C}
denote sets. Prove the following identities.
A
∪
∅
=
A
,
{\displaystyle {}A\cup \emptyset =A\,,}
A
∩
∅
=
∅
,
{\displaystyle {}A\cap \emptyset =\emptyset \,,}
A
∩
B
=
B
∩
A
,
{\displaystyle {}A\cap B=B\cap A\,,}
A
∪
B
=
B
∪
A
,
{\displaystyle {}A\cup B=B\cup A\,,}
A
∩
(
B
∩
C
)
=
(
A
∩
B
)
∩
C
,
{\displaystyle {}A\cap (B\cap C)=(A\cap B)\cap C\,,}
A
∪
(
B
∪
C
)
=
(
A
∪
B
)
∪
C
,
{\displaystyle {}A\cup (B\cup C)=(A\cup B)\cup C\,,}
A
∩
(
B
∪
C
)
=
(
A
∩
B
)
∪
(
A
∩
C
)
,
{\displaystyle {}A\cap (B\cup C)=(A\cap B)\cup (A\cap C)\,,}
A
∪
(
B
∩
C
)
=
(
A
∪
B
)
∩
(
A
∪
C
)
,
{\displaystyle {}A\cup (B\cap C)=(A\cup B)\cap (A\cup C)\,,}
A
∖
(
B
∪
C
)
=
(
A
∖
B
)
∩
(
A
∖
C
)
.
{\displaystyle {}A\setminus (B\cup C)=(A\setminus B)\cap (A\setminus C)\,.}
Disjoint sets/Moving/Bijection/Exercise
Sketch the set
M
=
{
(
x
,
y
)
∈
R
2
∣
4
x
−
7
y
=
3
}
{\displaystyle {}M={\left\{(x,y)\in \mathbb {R} ^{2}\mid 4x-7y=3\right\}}}
and the set
N
=
{
(
x
,
y
)
∈
R
2
∣
3
x
+
2
y
=
5
}
{\displaystyle {}N={\left\{(x,y)\in \mathbb {R} ^{2}\mid 3x+2y=5\right\}}}
.
Determine the intersection
M
∩
N
{\displaystyle {}M\cap N}
geometrically and arithmetically.
Space/Plane equation/Example for intersection/2/Exercise
Linear equation/Integers/Possibilities/1/Exercise
Product set/Geometric examples/Exercise
Let
M
{\displaystyle {}M}
and
N
{\displaystyle {}N}
denote sets and let
A
⊆
M
{\displaystyle {}A\subseteq M}
and
B
⊆
N
{\displaystyle {}B\subseteq N}
be subsets. Show the identity
(
A
×
N
)
∩
(
M
×
B
)
=
A
×
B
.
{\displaystyle {}{\left(A\times N\right)}\cap {\left(M\times B\right)}=A\times B\,.}
Product set/Distributivity law/Exercise
Product set/Binomial formula/Exercise
Hand-in-exercises
Several subsets im R^2/Sketch/2/Exercise
Real plane/Line equation/Sketch and intersection/2/Exercise
Does the "subtraction rule“ hold for the union of sets, i.e., can we infer from
A
∪
C
=
B
∪
C
{\displaystyle {}A\cup C=B\cup C}
that
A
=
B
{\displaystyle {}A=B}
holds?
Prove the following (settheoretical versions of) syllogisms of Aristotle. Let
A
,
B
,
C
{\displaystyle {}A,B,C}
denote sets.
Modus Barbara:
B
⊆
A
{\displaystyle {}B\subseteq A}
and
C
⊆
B
{\displaystyle {}C\subseteq B}
imply
C
⊆
A
{\displaystyle {}C\subseteq A}
.
Modus Celarent:
B
∩
A
=
∅
{\displaystyle {}B\cap A=\emptyset }
and
C
⊆
B
{\displaystyle {}C\subseteq B}
imply
C
∩
A
=
∅
{\displaystyle {}C\cap A=\emptyset }
.
Modus Darii:
B
⊆
A
{\displaystyle {}B\subseteq A}
and
C
∩
B
≠
∅
{\displaystyle {}C\cap B\neq \emptyset }
imply
C
∩
A
≠
∅
{\displaystyle {}C\cap A\neq \emptyset }
.
Modus Ferio:
B
∩
A
=
∅
{\displaystyle {}B\cap A=\emptyset }
and
C
∩
B
≠
∅
{\displaystyle {}C\cap B\neq \emptyset }
imply
C
⊈
A
{\displaystyle {}C\not \subseteq A}
.
Modus Baroco:
B
⊆
A
{\displaystyle {}B\subseteq A}
and
B
⊈
C
{\displaystyle {}B\not \subseteq C}
imply
A
⊈
C
{\displaystyle {}A\not \subseteq C}
.
Let
M
{\displaystyle {}M}
and
N
{\displaystyle {}N}
denote sets and let
A
1
,
A
2
⊆
M
{\displaystyle {}A_{1},A_{2}\subseteq M}
and
B
1
,
B
2
⊆
N
{\displaystyle {}B_{1},B_{2}\subseteq N}
be subsets. Show the identity
(
A
1
×
B
1
)
∩
(
A
2
×
B
2
)
=
(
A
1
∩
A
2
)
×
(
B
1
∩
B
2
)
.
{\displaystyle {}{\left(A_{1}\times B_{1}\right)}\cap {\left(A_{2}\times B_{2}\right)}={\left(A_{1}\cap A_{2}\right)}\times {\left(B_{1}\cap B_{2}\right)}\,.}
Let
A
{\displaystyle {}A}
and
B
{\displaystyle {}B}
be sets. Show that the following facts are equivalent.
A
⊆
B
{\displaystyle {}A\subseteq B}
,
A
∩
B
=
A
{\displaystyle {}A\cap B=A}
A
∪
B
=
B
{\displaystyle {}A\cup B=B}
,
A
∖
B
=
∅
{\displaystyle {}A\setminus B=\emptyset }
,
There exists a set
C
{\displaystyle {}C}
such that
B
=
A
∪
C
{\displaystyle {}B=A\cup C}
,
There exists a set
D
{\displaystyle {}D}
such that
A
=
B
∩
D
{\displaystyle {}A=B\cap D}
.