Post on 23-Jan-2018
Unit 09 May
1. DEFINITION OF A FUNCTION.
A Function is a relation between two Variables such that for every value of the
first, there is only one corresponding value of the second. We say that the second
variable is a Function of the first variable. The first variable is the Independent
Variable (usually ππ), and the second variable is the Dependent Variable (usually ππ).
The independent variable and the dependent variable are real numbers.
Example 1:
You know the formula for the area of a circle is π΄π΄ = ππππ2. This is a function as each
value of the independent variable ππ gives you one value of the dependent variable π΄π΄.
Example 2:
In the equation π¦π¦ = π₯π₯2, ππ is a function of ππ, since for each value of π₯π₯, there is only
one value of π¦π¦
Axel CotΓ³n GutiΓ©rrez Mathematics 4ΒΊ ESO 4.9.1
Unit 09 May
We normally write Functions as ππ(ππ), and read this as βfunction ππ of ππβ.
For example, the function π¦π¦ = π₯π₯2 β 5π₯π₯ + 2, is also written as ππ(π₯π₯) = π₯π₯2 β 5π₯π₯ + 2 (y
and f(x) are the same).
The Value of the Function ππ(ππ) when ππ = ππ is ππ(ππ).
If ππ(π₯π₯) = π₯π₯2 β 5π₯π₯ + 2, then ππ(2) = 22 β 5 β 2 + 2 = β4
A good way of presenting a function is by Graphical Representation. Graphs
give us a visual picture of the function. Normally, the values of the independent
variable (generally the x-values) are placed on the horizontal axis, while the values of
the dependent variable (generally the y-values) are placed on the vertical axis.
MATH VOCABULARY: Function, Independent Variable, Dependent Variable, Graph.
Axel CotΓ³n GutiΓ©rrez Mathematics 4ΒΊ ESO 4.9.2
Unit 09 May
2. ELEMENTARY FUNCTIONS.
LINEAR FUNCTIONS. 2.1.
A function that can be graphically represented in the Cartesian Coordinate
Plane by a straight line is called a Linear Function. The equation of a linear function is
ππ = ππππ + ππ
ππ is the Slope of the line and ππ is the y-intercept. Remember that if ππ > ππ ,
the line is an Increasing Function, and if ππ < ππ , the line is a Decreasing Function.
If ππ = ππ , the equation of the function ππ = ππ .This type of linear functions are
called Constant Functions. Their graphs are horizontal lines.
Axel CotΓ³n GutiΓ©rrez Mathematics 4ΒΊ ESO 4.9.3
Unit 09 May
If ππ = ππ , the equation of the function is ππ = ππππ, This type of linear functions
are called Proportional Functions. The variable β β is directly proportional to βππ β. The ππ
constant ratio ππ = ππ/ππ is called Proportionality Constant (or constant of
proportionality). Their graphs pass through the point (ππ,ππ).
If ππ = ππ, the proportionality function is ππ = ππ , and it is Called Identity
Function. This line is the Angle Bisector of the first and third quadrants.
Axel CotΓ³n GutiΓ©rrez Mathematics 4ΒΊ ESO 4.9.4
Unit 09 May
PARABOLAS AND QUADRATIC FUNCTIONS. 2.2.
A function whose graph is a Parabola is called a Quadratic Function. The
equation of a quadratic function is:
ππ = ππππππ + ππππ + ππ, ππ β ππ
A Parabola will have either an Absolute Minimum or an Absolute Maximum.
This point is called the Vertex of the parabola. There is a Line of Symmetry which will
divide the graph into two halves. This line is called the Axis of Symmetry of the
parabola.
Axel CotΓ³n GutiΓ©rrez Mathematics 4ΒΊ ESO 4.9.5
Unit 09 May
If two Quadratic Functions have the same βππβ, the corresponding parabolas are
equal, but they are placed in different positions.
The parabola will open upward or downward. If ππ > ππ , the parabola opens
Upward. If ππ < ππ , the parabola opens Downward.
The greater is |ππ| , the slimmer the parabola will be:
Axel CotΓ³n GutiΓ©rrez Mathematics 4ΒΊ ESO 4.9.6
Unit 09 May
A Parabola ππ = ππππππ + ππππ + ππ can be represented from these points:
Axes Intercept Points.
β’ ππ β ππππππππππππππππππππ: An x-intercept is a point on the graph where ππ = ππ. If
ππ = ππ β ππππππ + ππππ + ππ = ππ. When we solve the equation we can have:
Two different real solutions: ππππ; ππππ. Then there are two x-intercept points
(ππππ,ππ) and (ππππ,ππ).
One double real solution: ππππ = ππππ. Then there is only one x-intercept
point: (ππππ,ππ).
No real solutions. Then the graph does not intercept the x-axis.
Axel CotΓ³n GutiΓ©rrez Mathematics 4ΒΊ ESO 4.9.7
Unit 09 May
To summarize we can say that it will depends on the Discriminant:
β’ ππ β ππππππππππππππππππ: is a point on the graph where ππ = ππ. If ππ = ππ β ππ = ππ. Then
the y-intercept point is (ππ,ππ)
Axel CotΓ³n GutiΓ©rrez Mathematics 4ΒΊ ESO 4.9.8
Unit 09 May
Vertex οΏ½π½π½ππ,π½π½πποΏ½.
π½π½ππ =βππππππ
To find π½π½ππ we need to calculate:
π½π½ππ = ππ(π½π½ππ) = πππ½π½ππππ + πππ½π½ππ + ππ
Once we have these
points we can Plot the graph:
The Basic Parabola is ππ = ππππ. The function is symmetrical about the x-axis. Its
vertex is the point (ππ,ππ) , which is also the absolute minimum. The graph has two
branches (one of them is decreasing and the other one is increasing).
Axel CotΓ³n GutiΓ©rrez Mathematics 4ΒΊ ESO 4.9.9
Unit 09 May
INVERSELY PROPORTIONAL FUNCTIONS. 2.3.
If the variables βππβ and βππβ are Inversely Proportional, then the functional
dependence between them is represented by the equation:
ππ =ππππ
; ππ = ππππππππππππππππ β ππ
LetΒ΄s start from the easiest one:
ππ =ππππ
Its graph is a Hyperbola. It has two branches. If we focus on the branch for > ππ
: As ππ increases, then ππ decreases to ππ. As ππ drops to ππ, then y increases to +β. The
ππ and ππ β ππππππππ are Asymptotes of the function. Asymptote is a line that a graph gets
closer and closer to, but never touches or crosses it.
In the general case the Inversely Proportional Functions are:
ππ =ππππ
Axel CotΓ³n GutiΓ©rrez Mathematics 4ΒΊ ESO 4.9.10
Unit 09 May
They are Hyperbolas whose Asymptotes are the coordinate axes:
RATIONAL FUNCTIONS. 2.4.
The Inversely Proportional Functions are a particular case of Rational
Functions. We will study the easiest case which equation is:
ππ =ππ
ππ β ππ+ ππ
If ππ = ππ = ππ βΉ π°π°.π·π·.ππ. They are Hyperbolas whose Asymptotes ARENΒ΄T the
coordinate axes:
The Asymptotes will depends on the values of ππ and ππ
Axel CotΓ³n GutiΓ©rrez Mathematics 4ΒΊ ESO 4.9.11
Unit 09 May
To plot the graph we have to know ππ, ππ and ππ. and find the Asymptotes and
draw them. Then we look for values on each branch with the help of a table. We study
the function taking in care of the value of ππ.
Axel CotΓ³n GutiΓ©rrez Mathematics 4ΒΊ ESO 4.9.12
Unit 09 May
RADICAL FUNCTIONS. 2.5.
A Radical Function is any function that contains a variable inside a Root. This
includes square roots, cubed roots, or any nth root.
ππ = ππβππππ + ππππ
LetΒ΄s start with the easiest one:
ππ = βππ
It is half a Parabola. If we square both sides of the function and isolate ππ, we
end up with the equation of the parabola in terms of ππ.
ππ = βππ β ππππ = ππ
The functions ππ = ππβππ + ππ and ππ = ππββππ + ππ are also half parabolas.
Axel CotΓ³n GutiΓ©rrez Mathematics 4ΒΊ ESO 4.9.13
Unit 09 May
EXPONENTIAL FUNCTIONS. 2.6.
Do you remember Compound Interest problems? This is an example of
Exponential Function (the variable βππβ is at the exponent of a power).
The easiest one is: ππ = ππππ. The base βππβ can be any positive real number,
ππ β ππ. Look at these graphs:
The graphs of the functions passes through the points (ππ,ππ) and (ππ,ππ). The
functions ππ = ππππππππππ; ππππ,ππ β β , are also exponential functions. Their graphs are
similar to the graph of ππ = ππππ.
The best thing about exponential functions is that they are so useful in real
world situations. Exponential Functions are used to model populations, carbon date
artifacts, help coroners determine time of death, compute investments, as well as
many other applications. If ππ > ππ, the function is increasing and if ππ < ππ , the function
is decreasing.
The functions with the equation:
Axel CotΓ³n GutiΓ©rrez Mathematics 4ΒΊ ESO 4.9.14
Unit 09 May
ππ = ππππ + ππ
Are also Exponential Functions. The graph ππ = ππππ + ππ can be obtained by
scrolling vertically the graph from the function ππ = ππππ.
The functions with the equation:
ππ = ππ(ππ+ππ)
Are also Exponential Functions.
The graph ππ = ππ(ππ+ππ) can be obtained by moving horizontally the graph from
the function ππ = ππππ.
Axel CotΓ³n GutiΓ©rrez Mathematics 4ΒΊ ESO 4.9.15
Unit 09 May
Axel CotΓ³n GutiΓ©rrez Mathematics 4ΒΊ ESO 4.9.16
Unit 09 May
LOGARITHMIC FUNCTIONS. 2.7.
The functions ππ = ππππππππ ππ are called Logarithmic Functions. The base β β can ππ
be any positive real number, ππ β ππ .
Look at the graphs of ππ = ππππ and ππ = ππππππππ ππ:
In general, if we have two functions, ππ(ππ) and ππ(ππ , where if ) (ππ,ππ) lies on the
graph of ππ(ππ , then the point ) (ππ,ππ) lies on the graph of ππ(ππ , we say that ) is the ππ
Inverse Function of and vice versa. The Inverse Function of ππ is denoted by ππ ππβππ
(read f inverse, not to be confused with exponentiation).
The graphs of the functions ππ = ππππ and ππ = ππππππππ ππ are symmetric with respect
to the line ππ = . In general, graphs of inverse functions, ππ and ππ ππβππ are symmetric
with respect to the line ππ = . ππ
Look now at the graphs of ππ = ππππππππ ππ and ππ = ππππππππππππ:
Axel CotΓ³n GutiΓ©rrez Mathematics 4ΒΊ ESO 4.9.17
Unit 09 May
We see that the graph of ππ = ππππππππ ππ passes through the points (ππ,ππ) and
(ππ ,ππ) If . ππ > ππ the graph will be more closed than if is greater. If ππ ππ < ππ < ππ the
graph will be more closed than if is smaller. If ππ ππ > , the function is increasing and if ππ
ππ < , the function is decreasing. ππ
If we have the function ππ = ππππππππ ππ + ππ, we obtain the graph scrolling the
graph ππ = ππππππππ ππ. If ππ > ππ the graph is scrolling up units, if ππ ππ < ππ the graph is
scrolling down units. ππ
Axel CotΓ³n GutiΓ©rrez Mathematics 4ΒΊ ESO 4.9.18
Unit 09 May
If we have the function ππ = ππππππππ(ππ + ππ) we obtain the graph obtained by
moving horizontally the graph ππ = ππππππππ ππ. If ππ > ππ the graph is moving left units, if ππ
ππ < ππ the graph is moving right units. ππ
Axel CotΓ³n GutiΓ©rrez Mathematics 4ΒΊ ESO 4.9.19
Unit 09 May
TRIGONOMETRIC FUNCTIONS. 2.8.
The Trigonometric Function ππ = ππππππ ππ give for any angle measured in radians,
its sine value.
The Trigonometric Function ππ = ππππππ ππ give for any angle measured in radians,
its cosine value.
MATH VOCABULARY: Cartesian Coordinate Plane, Linear Function, Slope, Increasing
Function, Decreasing Function, Constant Function, Proportional Function, Identity
Function, Angle Bisector, Parabola, Quadratic Function, Absolute Minimum, Absolute
Maximum, Vertex, Line of Symmetry, Axis of Symmetry, To Plot, Inversely Proportional
Function, Hyperbola, Asymptotes, Rational Function, Radical Function, Exponential
Function, Logarithmic Function, Inverse Function, Trigonometric Function. Axel CotΓ³n GutiΓ©rrez Mathematics 4ΒΊ ESO 4.9.20
Unit 09 May
3. DOMAIN AND RANGE.
The Domain of a function is the complete set of possible values of the
independent variable in the function. The Range (or Image) of a function is the
complete set of all possible resulting values of the dependent variable of a function,
after we have substituted the values in the domain.
π«π«ππππππππππ ππππ ππ = π«π«ππππππ
π°π°ππππππππ ππππ ππ = π°π°ππππ
LINEAR FUNCTIONS. 3.1.
The Domain of a Linear Function is . The Range is usually also β β Only if .
ππ = ππ the Range is, [ππ,ππ]
Axel CotΓ³n GutiΓ©rrez Mathematics 4ΒΊ ESO 4.9.21
Unit 09 May
PARABOLAS AND QUADRATIC FUNCTIONS. 3.2.
The Domain of a Quadratic Function is . The Range is depending of the β
Vertex position.
INVERSELY PROPORTIONAL FUNCTIONS. 3.3.
The Domain of a Inversely Proportional Function is ββ {ππ . The Range is also }
ββ {ππ}.
Axel CotΓ³n GutiΓ©rrez Mathematics 4ΒΊ ESO 4.9.22
Unit 09 May
RATIONAL FUNCTIONS. 3.4.
Remember that
ππ =ππ
ππ β ππ+ ππ
The Domain is β β {ππ . The Range is } β β {ππ}.
Axel CotΓ³n GutiΓ©rrez Mathematics 4ΒΊ ESO 4.9.23
Unit 09 May
RADICAL FUNCTIONS. 3.5.
Remember that:
ππ = ππβππππ + ππππ
The Domain of Radical Functions depends on the value of on the radicand. ππ
The Range in the functions seen is always [ππ,β) if ππ > ππ and (ββ,ππ] if ππ < ππ.
EXPONENTIAL FUNCTIONS. 3.6.
The Domain of the functions ππ = ππππ, ππ = ππππ + ππ and ππ = ππ(ππ+ππ)is β The .
the functions ππ = ππππ and ππ = ππ(ππ+ππ)isRange of [ππ,β), the of ππ = ππππ + ππ will Range
depends on the value of . ππ
Axel CotΓ³n GutiΓ©rrez Mathematics 4ΒΊ ESO 4.9.24
Unit 09 May
LOGARITHMIC FUNCTIONS. 3.7.
If we have the function ππ = ππππππππ(ππ + ππ) the Domain is depending on the
value of .ππ The function ππ = ππππππππ ππ + ππ has as Domain (ππ,β). The Range of all of
them will be β .
The domain of is the range of ππ ππβ , and vice versa, the range of ππ is the ππ
domain of ππβππ .
Axel CotΓ³n GutiΓ©rrez Mathematics 4ΒΊ ESO 4.9.25
Unit 09 May
TRIGONOMETRIC FUNCTIONS. 3.8.
The Domain of ππ = ππππππ ππ and ππ = ππππππ ππ is β The Range is always [βππ,ππ]. .
MATH VOCABULARY: Domain, Range, Image.
4. CONTINUOUS AND DISCONTINUOUS FUNCTIONS.
Consider the graph of ππ = ππππππ ππ:
We can see that there are no βgapsβ in the curve. Any value of β β will give us a ππ
corresponding value of β β. We could continue the graph in the negative and positive y
directions, and we would never need to take the pencil off the paper. Such functions
are called Continuous Functions. Axel CotΓ³n GutiΓ©rrez Mathematics 4ΒΊ ESO 4.9.26
Unit 09 May
Now consider the function
ππ =ππ
ππ β ππ
We can see that the curve is discontinuous at ππ = ππ We observe that a small .
change in ππ near to ππ = , gives a very large change in the value of the function. ππ
x y 1.99 -199 2.01 201
For a function to be Continuous at a point, the function must exist at the point
and any small change in β β produces only a small change in βππ ππ(ππ β. If a function is not )
continuous at a point, we say that it is Discontinuous at that point.
A function ππ is Continuous on the Open Interval (ππ,ππ if ) is continuous at ππ
every point in (ππ,ππ . There are different reasons why a function is Discontinuous at a )
point. The four functions below are discontinuous at ππ = ππ.
Axel CotΓ³n GutiΓ©rrez Mathematics 4ΒΊ ESO 4.9.27
Unit 09 May
The function has a βFinite Jumpβ.
The function is βMissingβ a point.
The function has an βInfinite Jumpβ.
The function has a βMovedβ point.
Axel CotΓ³n GutiΓ©rrez Mathematics 4ΒΊ ESO 4.9.28
Unit 09 May
All the functions seen are Continuous except the Rational Functions that are
Discontinuous. The discontinuous point will be in the asymptote point.
MATH VOCABULARY: Continuous Function, Discontinuous Function, Finite Jump,
Infinite Jump.
5. INTERSECTION POINTS WITH THE AXIS.
The Intersection Points, are the ππ β ππππππππππππππππππ and ππ β points. ππππππππππππππππππ
The ππ β ππππππππππππππππππ points can be calculated by solving the equation when ππ = ππ And .
the ππ β ππππππππππππππππππ points can be calculated by solving the equation when ππ = ππ.
The ππ β ππππππππππππππππππ points are always (ππ,ππ , and the) ππ β ππππππππππππππππππ are
always (ππ,ππ).
Example 1:
π¦π¦ = β5π₯π₯ + 2
π₯π₯ β ππππππππππππππππππ β ππ(π₯π₯) = 0
0 = β5π₯π₯ + 2
π₯π₯ =25
π₯π₯ β ππππππππππππππππππ β οΏ½25
, 0οΏ½
π¦π¦ β ππππππππππππππππππ β ππ(0)
π¦π¦ = β5 β 0 + 2 = 2
π¦π¦ β ππππππππππππππππππ β (0,2)
Example 2:
π¦π¦ = π₯π₯2 + π₯π₯ β 6
Axel CotΓ³n GutiΓ©rrez Mathematics 4ΒΊ ESO 4.9.29
Unit 09 May
π₯π₯ β ππππππππππππππππππ β ππ(π₯π₯) = 0
0 = π₯π₯2 + π₯π₯ β 6
π₯π₯ =β1 Β± οΏ½12 β 4 β 1 β (β6)
2= οΏ½ π₯π₯1 = 2
π₯π₯2 = β3
π₯π₯ β ππππππππππππππππππ β (2,0) ππππππ (β3,0)
π¦π¦ β ππππππππππππππππππ β ππ(0)
π¦π¦ = 02 + 0 β 6 = β6
π¦π¦ β ππππππππππππππππππ β (0,6)
Remember that in Exponential Functions like ππ(ππ) = ππ , the ππ ππ β ππππππππππππππππππ is
always (ππ,ππ and in Logarithmic Functions as ) ππ(ππ) = π₯π₯π₯π₯π₯π₯ππ ππ the ππ β ππππππππππππππππππ is
always (ππ,ππ) In the Basic Sine Function the . ππ β ππππππππππππππππππ points are those whose
π¬π¬π¬π¬π¬π¬π½π½ = , and the ππ ππ β ππππππππππππππππππ is always (ππ,ππ) In the Basic Cosine Function the .
ππ β ππππππππππππππππππ points are those whose πππ₯π₯π¬π¬π½π½ = , and the ππ ππ β ππππππππππππππππππ is always
(ππ,ππ) .
MATH VOCABULARY: Intersection Points.
6. VARIATIONS IN A FUNCTION.
INCREASING AND DECREASING. 6.1.
A function is Increasing on an interval ππ (ππ,ππ) if for any ππππ and ππ in the ππ
interval such that ππππ < ππππ then ππ(ππππ) < ππ(ππππ . Another way to look at this is: as you )
trace the graph from to ππ (that is from left to right) the graph should go up. ππ
Axel CotΓ³n GutiΓ©rrez Mathematics 4ΒΊ ESO 4.9.30
Unit 09 May
A function is Decreasing on an interval ππ (ππ,ππ) if for any ππππ and ππ in the ππ
interval such that ππππ < ππππ then ππ(ππππ) > ππ(ππππ . Another way to look at this is: as you )
trace the graph from to ππ (that is from left to right) the graph should go down. ππ
Axel CotΓ³n GutiΓ©rrez Mathematics 4ΒΊ ESO 4.9.31
Unit 09 May
Axel CotΓ³n GutiΓ©rrez Mathematics 4ΒΊ ESO 4.9.32
Unit 09 May
MAXIMA AND MINIMA. 6.2.
A function has a Relative (or Local) Maximum at a point if its ordinate is ππ
greater that the ordinates of the points around it. A function has a Relative (or Local) ππ
Minimum at a point if its ordinate is smaller than the ordinates of the points around it.
A function has an Absolute (or Global) Maximum at a point if its ordinate is ππ
the largest value that the function takes on the domain that we are working on. A
function has an Absolute (or Global) Minimum at a point if its ordinate is smallest ππ
value that the function takes on the domain that we are working on.
MATH VOCABULARY: Increasing Function Decreasing Function, Relative Maximum,
Relative Maximum, Absolute Maximum, Absolute Minimum.
Axel CotΓ³n GutiΓ©rrez Mathematics 4ΒΊ ESO 4.9.33
Unit 09 May
7. PERIODIC FUNCTIONS.
A Periodic Function repeats Cycle may begin at any point on the graph of the
function. The Period of a function is the horizontal length a pattern of ππ β ππππππππππππ at
regular intervals. One complete pattern is a Cycle.
If ππ is a Periodic Function whose Period is π·π·, then ππ(ππ + ππ β π·π·) = ππ(ππ) for all
values of ππ.
The Amplitude of a periodic function measures the amount of variation in the
function values.
The Amplitude of a periodic function is half the difference between the
maximum and minimum values of the function.
Axel CotΓ³n GutiΓ©rrez Mathematics 4ΒΊ ESO 4.9.34
Unit 09 May
The only Periodic Functions studied are the Trigonometric Functions seen.
MATH VOCABULARY: Periodic Function, Cycle, Period, Amplitude.
Axel CotΓ³n GutiΓ©rrez Mathematics 4ΒΊ ESO 4.9.35
Unit 09 May
8. SYMMETRIC FUNCTIONS.
There are two kinds of Symmetric Functions:
β’ Symmetric Function respect to the Y-Axis: ππ(βππ) = ππ(ππ). It is also called Even
Function.
Axel CotΓ³n GutiΓ©rrez Mathematics 4ΒΊ ESO 4.9.36
Unit 09 May
β’ Symmetric Function respect to Origin: ππ(βππ) = βππ(ππ). It is also called Odd
Function.
To study the symmetry of a function we have to calculate ππ(βππ) and compare
the result with ππ(ππ).
MATH VOCABULARY: Symmetric Function, Even Function, Odd Function.
Axel CotΓ³n GutiΓ©rrez Mathematics 4ΒΊ ESO 4.9.37