There are 3types of angle
Let’s take a look at the clocks
showing the respective times
Lola Remy, Lola Inday and Lola
Nancy take their vitamins.
13.
At 9:00, theminute and hour hands of the
clock form an angle which measures 90˚.
This angle, like all angles which measure
90˚, is called a right angle.
14.
At 2:00, theminute and hour hands of
the clock form an angle which
measures 60˚. This is between 0˚ and
90˚ The angle here, like all other
angles which measure between 0˚
and 90˚, is called an acute angle.
15.
At 5:00, theminute and hour hands of the
clock form an angle which measures
150˚. This is between 90˚ and 180˚ The
angle here, like all other angles which
measure between 90˚ and 180˚, is called
an obtuse angle.
16.
An angle isformed by
two rays with a
common endpoint.
17.
In the figurebelow, Rays BA
and BC have B as their
common endpoint and they
form angle ∠ABC. Using
symbols, we write , which is read
as “angle ABC”. The angle may
also be called ∠CBA.
1. Which anglemeasures 90 degrees and
forms a square corner?
A. acute angle B. right angle
C. obtuse angle D. straight angle
2. Which angle measures less than 90 degrees
and smaller than a right angle?
A. acute angle B. right angle
C. obtuse angle D. straight angle
26.
3. Which anglemeasures more
than 90 degrees?
A. acute angle B. right angle
C. obtuse angle D. straight angle
4. Which of the following is a
measure of an obtuse angle?
A. 70° B. 90° C. 120° D. 180°
27.
5. What geometricfigure is
formed when two rays meet
at a common endpoint?
A. angle B. line
C. point D. ray
28.
Identify the kindof angle
represented by each of
the following figure. Write
the correct answer on a
sheet of paper.
Let us tryto see the ways to right an angle
There are three ways to name angles.
40.
Degrees is aunit of measurement angles,
one three-hundred and-sixtieth (1/360) of
the circumference of a circle. The degree
symbol or degree sign, (°) is a
typographical symbol that is used,
among other things, to represent degrees
of arc.
To measure angles, we use the unit called
degrees
42.
• As themeasure of an angle
increases, the name changes.
• Angles are the figure formed by two
rays, called the sides of an
angle, sharing a common endpoint,
called the vertex of the angle.
• Angles are measured in degrees (°),
using a protractor.
43.
• Angles canbe classified according
to their measurements.
• An acute angle measures less than
90°. It is smaller than a right angle.
• A right angle measures 90°. It forms
a square corner.
• An obtuse angle measures more
than 90° but less than 180°.
44.
Let us alwaysremember that
A right angle measures exactly 90˚.
An acute angle measures between
0 ˚ and 90 ˚. An obtuse angle
measures between 90 ˚ and 180 ˚
Ask the pupils;
Whatare the 3 ways in naming
angles?
What are the 3 types of angles?
48.
Using the figureat the right,
identify if the given angle is
acute, right or obtuse. Write
the correct answer on a
sheet of paper.
50.
Let’s try thisexercise
Use the data inside the box to
complete the statement. Write your
answer on a sheet of paper.
51.
When two raysmeet a common endpoint, a
geometric figure called (1.) _______ is formed. The
common endpoint is called the (2.) ______ . Angles
are measured in (3.) _______ and can be classified
according to their measurements. An angle which
measures 90° and forms a square corner is called
the (4.) ___________. If it measures less than 90° and
is smaller than a right angle, it is called the (5.)
___________. If it measures more than 90° but less
than 180°, it is called (6.) ___________.
A protractor isused for measuring
angles. As shown above, a protractor
is a half or full circle measuring device,
marked in degrees along the outer
edge, with a straight line running from
0° to 180°. There is a small hole in the
center of the protractor.
61.
Let us tryto look back the concept of
rays to know more about protractor
The concept of rays is useful for us to
effectively grasp the lesson. Let us first
learn about rays.
62.
A ray isa part of a line with an endpoint
and extends endlessly in one direction. It is
named by its endpoint and any other
point on it.
63.
Figure 1 showsan example of a
ray. Ray AB has endpoint A and
goes indefinitely toward the
direction of point B. A ray with an
endpoint A and another point B on
one side of endpoint A is named
AB (read as “ray AB”).
64.
Note that rayAB cannot be called BA. Ray BA has
an endpoint B, as illustrated in Figure 3 below.
Figure 2: The given ray is called BA
The measure ofan angle indicates
how wide the opening is between
its two sides. A protractor is used to
find the measure of an angle, just
like a ruler is used to find the length
of a segment.
67.
protractor over thevertex of an angle. Then align the
mark labeled 0 with one side of the angle and read the
scale where the other side of the angle falls. The unit of
measurement used for angles is called degree, denoted
by the symbol °.
68.
A protractor usuallyhas outer and inner degree
scales. You may use any of these scales
depending on the positions of the angle. Using
the inner scale of the protractor shown in the
figure above, the measure of ∠𝐺𝐸𝑂 is equal to
50 °, written as
69.
Now, let ustry to draw ∠𝐿𝐴𝐵 so that 𝑚∠𝐿
𝐴𝐵 = 80° . Use a protractor.
70.
Let us trythis
Estimate the measure of each angle. Classify the
angles whether RIGHT, ACUTE or OBTUSE ANGLE.
How are yougoing to
measure angle using a
protractor?
82.
Can you recallwhat you see
at home or on your way to
school the angles that you
find or see?
83.
Angles can befound everywhere.
Buildings, establishments, satellite dishes,
billboards, and many other objects forming
angles. Of course, you also have clocks in
your homes, right? Notice the figure
formed by the two hands of the clock.
They are clearly examples of angles. These
sounds interesting. Hello, angles!
84.
Do you haveyour protractor with you?
Today, we are going to use that in
measuring angles.
Let’s do this together.
(The teacher demonstrates how to measure
the angle using a protractor)
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