Module 1
Module 1
Module 1
WORLD
GNED - 03
FIRST MODULE
LEARNING OBJECTIVES:
Recall that symmetry indicates that you can draw an imaginary line across an object and the
resulting parts are mirror images of each other.
A figure has a rotational symmetry of order n (n-fold rotational symmetry) if 1/n of a complete
turn leaves the figure unchanged. To compute for the angle of rotation, we use the following
formula:
Angle of rotation = 360°/𝑛
Order of Rotation
Order of Rotation
It can be observed that the patterns on a snowflake repeat six times, indicating that there is a
six-fold symmetry. To determine the angle of rotation, we simply divide 360° by 6 to get 60°.
Many combinations and complex shapes of snowflakes may occur, which lead some people to
think that “no two are alike”. If you look closely, however, many snowflakes are not perfectly
symmetric due to the effects of humidity and temperature on the ice crystal as it forms.
Another marvel of nature’s design is the structure and shape of a honeycomb. People have
long wondered how bees, despite their very small side, are able to produce such arrangement
while human would generally need the use of a ruler and compass to accomplish the same feat.
It is observed that such formation enables the bee colony to maximize their storage of honey
using the smallest amount of wax.
You can try it out for yourself. Using several coins of the same size, try to cover as much area
od a piece of paper with coins. If you arrange the coins in a square formation, there are still
plenty of spots that are exposed. Following the hexagonal formation, however, with the
second row of coins snugly fitted between the first row of coins, you will notice that more
area will be covered.
Translating this idea to three-dimensional space, we can conclude that hexagonal that
hexagonal formations are more optimal in making use of the available space. These are referred
to as packing problem. Packing problems involve finding the optimum method of filling up a
given space such as a cubic or spherical container. The bees have instinctively found the best
solution, evident in the hexagonal construction of their hives. These geometric patterns are not
only simple and beautiful, but also optimally functional.
Let us illustrate this mathematically. Suppose you have circles of radius 1 cm, each of which
will then have an area of 𝜋𝑐𝑚²
. We are then going to fill a plane with these circles using square
packing and hexagonal packing.
For square packing, each square will have an area of 4𝑐𝑚2
.Note from the figure that for each square, it can fit only one circle (4
quarters). The percentage of the square’s area covered by circles will
be
This gives the area of the hexagon as 6√3𝑐𝑚². Looking at the figure,
there are 3 circles that could fit inside one hexagon (the whole
circle in the middle, and 6 one thirds of a circle), which gives the
total area as 3𝜋𝑐𝑚². The percentage of the hexagon’s area
covered by circles will be
Patterns are exhibited in the external appearances of animals. We are familiar with
how a tiger looks-distinctive reddish-orange fur and dark stripes. Hyenas, another
predator from Africa, are also covered in patterns of spots. These seemingly random
designs are believed to be governed by mathematical equations. According to a
theory by Alan Turing, the man famous for breaking the Enigma code during World
War 11, chemical reactions and diffusion processes in cells determine these growth
patterns. More recent studies addressed the question of why some species grow
vertical stripes while others have horizontal ones. A new model by Harvard University
researchers predicts that there are three variables that could affect the orientation
of these stripes-the substance that amplifies the density of stripe pattern; the
substance that changes one of the parameters involved in stripe formation; and the
physical change in the direction of the origin of the stripe.
Tigers’ Stripes and Hyenas’ Spots
The Sunflower
We are also very familiar with spiral patterns. The most common
spiral patterns can be seen in whirlpools and in the shells of snails
and other similar mollusks. Snails are born with their shells, called
protoconch, which start out as fragile and colorless. Eventually,
these original shells harden as the snails consume calcium. As the
snails grow, their shells also expand proportionately so that they
can continue to live inside their shells. This process resulted in a
refined spiral structure that is even more visible when the shell is
sliced. This figure, called an equiangular spiral, follows the rule that
as the distance follows the rule that as the distance from the spiral
center increase (radius), the amplitudes of the angles formed by
the radii to the point and the tangent to the point remain
constant. this is another example of how nature seems follow a
certain set of rules governed by mathematics.
Flower Petals
Flower Petals
Flowers are considered as things of beauty. Their vibrant colors and fragrant colors and
fragrant odor make them vey appealing as gifts or decorations. If you look more closely, you
will note that different flowers have different number of petals. Take the iris and trillium, for
example. Both flowers have only 3 petals.
Flowers with five petals are said to be the most common. These include buttercup,
columbine, and hibiscus. Among those flowers with eight petals are clematis and delphinium,
while ragwort and marigold have thirteen. These numbers are all Fibonacci numbers, which
we will discuss in detail in the next section.
World Population
As of 2017, it is estimated that the world population is about 7.6 billion. World leaders,
sociologists, and anthropologists are interested in studying population, including its growth.
Mathematics can be used to model population growth. Recall that the formula for
exponential
growth 𝐴 = 𝑃𝑒𝑟𝑡, where A is the size of the population after it grows, P is the initial number
of people, r is the rate growth, and t is time. Recall further that e is Euler’s constant with an
approximate value of 2.718. plugging in values to this formula would result in the population
size after time t with a growth rate of r.
Example 3 Population Growth
The exponential growth model 𝐴 = 30𝑒0.02𝑡 describes the population of a city in the Philippines in thousands, t years after 1995.
a. What was the population of the city in 1995?
b. What will be the population in 2017?
Solution
a. Since our exponential growth model describes the population t years after 1995, we
considered 1995 as 𝑡 = 0 and then solve for A, our population size.
A = 30𝑒0.02𝑡
A = 30𝑒(0.02)(0)
Replace t with t = 0
A = 30𝑒0
A = 30(1) 𝑒0 = 1
A = 30
Therefore, the city population in 1995 was 30,000
Example 3 Population Growth
b. We need find A for the year 2017. To find t, we subtract 2017 and 1995 to get t = 22,
which we then plug in to our exponential growth model.
A = 30𝑒0.02𝑡
A = 30𝑒(0.02)(22)
Replace t with t = 22
A = 30𝑒0.44
A = 30(1.55271) 𝑒0.44 =1.55271
A = 46.5813
EXERCISE SET
EXERCISE SET:
as we have seen in the previous section, the human mind is hardwired to recognize
patterns. In mathematics, we can generate patterns by perming one or several
mathematical operations repeatedly. Suppose we choose the number 3 as the first
number in our pattern. We then choose to add 5 to our first number, resulting in 8,
which is our second number. Repeating this process, we obtain 13, 18, 23, 28, . . . as
the succeeding numbers that form our pattern. In mathematics, we call these ordered
lists of numbers a sequence.
Sequence
A sequence is an ordered list of numbers, called terms, that may have repeated values.
The arrangement of these terms is set by a definite rule.
Example 1 Generating Sequence
Analyze the given sequence for its rule and identify the next three terms
a. 1, 10, 100, 1000
b. 2, 5, 9, 14, 20
Solution
a. Looking at the set of numbers., it can be observed that each term is a power of 10:
1=100, 10 =101, 100 = 102, and 1000 = 103. Following this rule, the next three terms are
104 = 10,000, 105 = 100,000, and 106 = 1,000,000.
b. The difference between the first and second terms (2 and5) is 3. The difference between
the second and third terms (5 and 9) is 4. The difference between the third and fourth
terms (9 and 14) is 5. The difference between the fourth and fifth terms is 6. Following
this rule, it can be deduced that to obtain the next three terms, we should add 7, 8, 9,
respectively, to the current term. Hence, the next three terms are 20 + 7 = 27, 27 + 8 =
35, 35 + 9 = 44.
The Fibonacci Sequence
It is named after the Italian mathematician Leonardo of Pisa, who was better known by
his
nickname Fibonacci. He is said to have discovered this sequence as he looked at how a
hypothesized group of rabbits bred and reproduced. The problem involved having a
single pair
of rabbits and then finding out how many pairs of rabbits will be born in a year, with the
assumption that a new pair of rabbits is born each month and this new pair, in turn, give
birth
to additional pairs of rabbits beginning at two months after they were born. He noted
that the
set of numbers generated from this problem could be extended by getting the sum of
the two
previous terms.
The Fibonacci Sequence
It is sometimes said that history repeats itself. As much as we can use mathematical models
using existing data to generate analysis and interpretations, we can also use them to make
predictions. Applying the concepts of probability,experts can calculate the chance of an
event occurring. The weather is prime example.Based on historical patterns,meteorologists
can make forecasts to help us prepare for our day-to-day activities. They can also warn us
of weather disturbances that can affect our activities for weeks or months. Astronomers also
use patterns to predict the occurrence of meteor showers or eclipses. In 2017
announcements were made about heavenly phenomena such as the Draconid Meteor
Shower and “The Great American Eclipse”. They were able to tell when these phenomena
would occur and where would be the best places to view them.
Mathematics for Prediction
Mathematics for Control