Chapter 2Relations and
Functions
Objectives
1. define relations, functions and inverse functions;
2. state the domain, range, intercepts and symmetry of the functions and relations;
3. differentiate relations from functions;4. perform operations on functions; and5. sketch the graphs of functions and their
inverses.
Chapter 2.0Cartesian
Coordinate System
Cross Product
cross product of Let and be nonempty sets.The is a
, a
n
nd
d A B
A B x y x A
B
y
A
B
Cartesian Coordinate System
2Consider , and
Each ordered pair of real numbers isassociated with a point in a plane.
x y x y
Ordered Pairs
Consider an ordered pair , which is
associated with point .
- x gives the directed distance of from the y axis.- y gives the directed distance of from the x axis.
x y
P
P
P
Cartesian Coordinate System
axisx
axisy
O
,x yx
y
Cartesian Coordinate System
c
I
o
f
or
a po
dina
int ,
tes
then and are
the
abscissaordinat
of .
:e:
P x y x y
P
xy
Example 2.0.1
Plot the following points.
1. 2,7
2. 0, 1
3. 4, 6
4. : with abscissa 3and ordinate 5
P
Q
R
S
2,7P
0, 1Q
4, 6R
3,5S
Quadrants
1st quadrant2nd Quadrant
3rd Quadrant 4th Quadrant
Distance Formula
1 1 2 2
2 22 1 2 1
The distance between two points
, and , is given byP x y Q x y
PQ x x y y
Midpoint
1 1
2 2
1 2 1 2
The midpoint of a line segment
between two points , and
, is
,2 2
P x y
Q x y
x x y y
Slope
1 1 2 2
2 1
2 1
The slope of the line containing
, and , isP x y Q x y
y ym
x x
Example 2.0.2
2 2
Given 2,7 and 2, 3 ,1. find the distance between and .
2 2 7 3
16 100116
4 29
2 29
P QP Q
PQ
Given 2,7 and 2, 3 ,2. find the midpoint of the segment
joining and .
2 2 7 3, 0,2
2 2
P Q
P Q
Given 2,7 and 2, 3 ,
3. determine the slope of the linesjoining and .
3 7 10 52 2 4 2
P Q
P Q
m
Chapter 2.1Relations
Relation
relation from to Let and be nonempty sets.A is any nonempty subset of .
A B
A
A
A BB
S
S B
Relation in
A relation in is any non-emptysubset of .
Example 2.1.1
1,1 , 2,4 , 3,9 , 4,16 , 5,25
is a relation from to .
S
12345
149
1625
Relation
A relation can also be described byequations and inequalities.
Example 2.1.2
2
2
, is a relation from the set
of nonegative real numbers to .
can also
dependent vari
be described by
is the is the
ableindependent variable
T r A A r
T A r
rA
Example 2.1.3
1
22
3
21
Following are relations from to .
1. , 2 5
2. ,
3. , 3
4. , 4 1
r x y y x
r x y y x
r x y y x
r x y x y
Domain
The of a relation : , denoted
by , is the set containing all the first
members of the or
dom
dered pai s
a
r .
in r A B
Dom r
Range
The of , denoted by or
is the set containing all the second
members of the ordered pairs
r
n .
e
i
ang r Range r
Rng r
r
Example 2.1.4
Identify the domain and range of therelation
1,1 , 2,4 , 3,9 , 4,16 , 5,25
1,2,3,4,5
1,4,9,16,25
S
Dom S
Rng S
Domain and Range
The domain is the set of all values of the independent variable
permisible
resulting
.
The range is the set of all values of the dependent variable.
Example 2.1.5
Identify the domain and range of thefollowing relations.
1. , 2 1S x y y x
Dom S
Rng S
2
2
2. ,
0,
3. , 4
4,
T x y y x
Dom T
Rng T
U x y y x
Dom U
Rng U
24. ,
11
0
5. , 1
1 0 1,
1 0,
V x y yx
Dom V
Rng V
W x y y x
x Dom W
x Rng W
26. ,
0,
0
7. , 2 3
0,
X x y x y
y x Dom X
x Rng X
Y x y y x
Dom Y
Rng Y
8. , 5 4
4,
9. , 5
0
0,
,5
Z x y y x
Dom Z
Rng Z
A x y y x
x
Dom A
Rng A
Graph of a Relation
The is the set
of all points , in a coordinate plane
such that is related to
graph of a re
through
l
t
a
h
t
erelati
n
io
on .
x y
x yr
r
Intercepts
is a point where the graphof a relation crosses the axis.
is a point where the graphof
i
a
nt
r
erce
elat
pt
inion crosses the axis.
tercept
x
y
x
y
Example 2.1.6
2 2
2
2
Find the and intercepts of
1
intercept: 1,0 , 1,0
if 0, 11
intercept: 0,1 , 0, 1
if 0, 11
x y
x y
x
y xx
y
x yy
Symmetries
The graph of an equation is symmetric
with respect to the axis if an
equivalent equation is obtained when
is replaced by .
,
,
SWRTY
x y
x y
y
Example 2.1.7
2 2
2 2
2 2
2 2
2 2
Show that the graph of 4is SWRTY.
4
replacing , by , we get
4
4
Therefore, the graph of 4is SWRTY.
x y
x y
x y x y
x y
x y
x y
,x y ,x y
Symmetries
The graph of an equation is symmetric
with respect to the axis if an
equivalent equation is obtained when
is replaced by .
,
,
SWRTX
x y
x y
x
Example 2.1.8
2
2
2
2
2
Show that the graph of 4is SWRTX.
4
replacing , by , we get
4
4
Therefore, the graph of 4is SWRTX.
x y
x y
x y x y
x y
x y
x y
,x y
,x y
Symmetries
The graph of an equation is symmetric
with respect to the origin if an
equivalent equation is obtained when
is replaced by
,
.,
SWRTO
x y
x y
Example 2.1.9
2 2
2 2
2 2
2 2
2 2
Show that the graph of 4is SWRTO.
4
replacing , by , we get
4
4
Therefore, the graph of 4is SWRTO.
x y
x y
x y x y
x y
x y
x y
,x y
,x y
Example 2.1.10
2
2
2
2
Given , 2 1 ,
1. Find the domain and range.
1,
0
2 0
2 1 1
r x y y x
Dom r Rng r
x
x
x
2
2
2
2
Given , 2 1 ,
2. Find the intercepts.
2 2intercept: ,0 , ,0
2 2
if 0, 0 2 1
2 112
1 222
r x y y x
x
y x
x
x
x
2Given , 2 1 ,
intercept: 0, 1
if 0 : 1
r x y y x
y
x y
2
2
2
2
Given , 2 1 ,
3. Identify the symmetries.SWRTY
2 1
replacing , by ,
2 1
2 1The graph is SWRTY.
r x y y x
y x
x y x y
y x
y x
2
2
2
Given , 2 1 ,
SWRTX
2 1
replacing , by ,
2 1
The graph is not SWRTX.
r x y y x
y x
x y x y
y x
2
2
2
2
Given , 2 1 ,
SWRTO
2 1
replacing , by ,
2 1
2 1
The graph is not SWRTO.
r x y y x
y x
x y x y
y x
y x
2Given , 2 1 ,
1,
Symmetry: SWRTYIntercepts:
2 2: ,0 , ,0
2 2
: 0, 1
r x y y x
Dom r
Rng r
x
y
x 1y 1
Special Graphs: Lines
: passing through ,0vertical line
horizontal lin
.
: passing through ,e 0 .
x a a
y a a
Example 2.1.11Sketch the graph of1. 3y
3y
2. 2x
2x
Lines
If the defining equation of a relationis both linear in and , the
linear relatiorelation
is called a and its graphis a
nstraight l e.in
x y
Example 2.1.12
Identify the and intercepts andsketch the graph of 2 5.
5intercept: ,0
2if 0 : 0 2 5
52
intercept: 0,5
if 0 : 2 0 5
5
x yy x
x
y x
x
y
x y
y
2 5y x
Special Graphs: Quadratic Curves
2
2
Parabola
: parabola openingupward if 0downward if 0
: parabola opening to theleft if 0right if 0
y ax ka
a
x ay kaa
Example 2.1.13
2Given 1, find the domain and rangethen sketch the graph.
Domain: 1,
Range:
x y
x 2 1 2y -1 0 1
Example 2.1.14
2Given 2, find the domain and rangethen sketch the graph.
Domain:
Range: 2,
y x
X -1 0 1y -1 -2 -1
Special Graphs
2 2 2
centered
Circle
at 0,0 radi
s
, 0
Circle wi u th .s
x y a
a
a
a
a
a
a
Domain: ,
Range: ,
a a
a a
Example 2.1.15
2 2Given 16, find the domain and rangethen sketch the graph.
Domain: 4,4
Range: 4,4
x y
Special Graphs
2 2
2 2
Ellipse
1
intercepts: ,0 , ,0
intercepts: 0, , 0,
Domain: ,
Range: ,
x ya bx a a
y b b
a a
b b
aa
b
b
Example 2.1.16
2 2
2 2
2 2
Given 4 9 36, find the domain and rangethen sketch the graph.
4 9 36
19 4
intercepts: 3,0 , 3,0
intercepts: 0,2 , 0, 2
Domain: 3,3
Range: 2,2
x y
x y
x y
x
y
Special Graphs
2 2
2 2
2 2 2 22
2 2 2
2 2
2 2
Hyperbola
1 intercepts: ,0 , ,0
Asymptotes:
0
x yx a a
a b
x y b xy
a b ay x b
y xb a a
Special Graphs
Hyperbola
intercepts: ,0 , ,0
Asymptotes:
Domain: , ,
Range:
x a a
by x
a
a a
aa
b
b
by x
a
by x
a
Example 2.1.17
2 2
2
2
Given 1, find the domain and range9 25
then sketch the graph.
intercept: 3,0 , 3,0
if 0, 19
93
x y
x
xy
xx
2 2
2
2
19 25
intercept: 3,0 , 3,0
intercept: none
if 0, 125
255
Asymptotes:3
x y
x
y
yx
y
y x
53
y x
53
y x
Domain: , 3 3,
Range: