MEASURES OF AN

ANGLES

LEARNING OBJECTIVES:

To be able to analyze and measure angles using a protractor .

To be able to identify angles as right angle, acute angle, obtuse angle, straight angle.

To be able to learn what is angle is.

Introduction:

Angles can be measured in degrees or radians. For the time being, we will strictly talk about angles in terms of their degree

measure. The symbol for degrees is °. Angles can measure from 0°up

to 360°. Angles with no measure are called zero angles, while

angles of 360° are full rotations.

ANGLESAn angles is a figure formed by two rays

with common endpoint , and which are not on

the same line. Two rays are called the

sides of the angle. The common endpoint of the sides of an angles is called the vertex.

O1

A

B

• In the figure above , rays OA and OB are the two sides of the angle. Point O is the vertex of the angle.

MEASURES OF ANGLESThe measures of an angle refers to the opening made from one side of the angle to the other. An arrow from one side of the angle to the other usually denotes the particular

measured desired.

40

B

C

40

B

C

To use the protractor, place the center point of the protractor on the vertex of the angle to be measured. Line up the marked label 0 on either scale with one side of the

angle . In the figure above, the measure of angle BAC is 40 degrees.

A

CLASSIFICATION OF ANGLES

Right Angle

• A right angle is an angle whose measure is exactly 90°

J

K

L

90

Acute Angle• An acute angle is an

angle whose measure is less than 90°

BA

C

E

D

F

Obtuse Angle• Obtuse angles have

measures greater than 90° but less than 180°.

Q

R

S

T U

V

Straight Angle

Q

P

R

180

• if an angle’s measure is 180°, it is called a straight angle.

ACTIVITY:A. Identify what is being modified in

FF.1. An angle whose measure is exactly 90°.

2. A figure formed by two rays with common endpoint.

RIGHT ANGLE

ANGLE3. An angle whose measure is 180 degrees.

STRAIGHT ANGLE

4. an angle whose measure is less than 90°.ACUTE ANGLE

5. angles have measures greater than 90° but less than 180°.OBTUSE ANGLE

EVALUATION:

A. Use your protractor to measure each angle in the given figure.

1. Angle JOK2. Angle KOM3. Angle LON4. Angle MOP5. Angle POL

6. Angle KOL7. Angle JOP8.Angle MOL

9. Angle MON10.Angle JOL

J O

P

KL M

N

EVALUATION:

B. (same figure) Tell what kind of angle is each.1. Angle JOK2. Angle KOM3. Angle LON4. Angle MOP5. Angle POL

J O

P

KL M

N

6. Angle KOL7. Angle JOP8.Angle MOL

9. Angle MON10.Angle JOL

ANSWERS:A. 1. 1352. 903. 904. 905. 1356. 457. 1358. 459. 4510.90

B.1. Obtuse angle2. Right angle3. Right angle4. Right angle5. Obtuse angle6. Acute angle7. Obtuse angle8. Acute angle9. Acute angle10.Right angle

Submitted by:Patricia Marie S. Enriquez

Submitted to: Ms. Filomena S. De Guzman

III-OSIAS