Measuring Angles, Read This
1. Measuring Angles with Non-standard Units
Try copying the following on thin paper ∠A. After that, measure ∠B with the copy of ∠A!
2. Measuring Angles with a Protractor The unit of angle is degrees (°).
The tool used to measure the size of an angle is a protractor. A protractor is a semicircle with a scale from 0° to 180°.
How do you measure the size of an angle with a protractor?
3. Know Right Angles
Try to follow the following series of activities! Come on, get a piece of paper. After that, fold the paper in half! The folded paper is then folded again, so that the first folded sides overlap. The angle at the last fold is called a right angle.
4. Direction of the Wind
Every day you see the sun rising in the morning and setting in the evening. From which direction does the sun rise? Which way does the sun set?
To answer the question above, of course you have to know the direction of the wind. The following are the names of the cardinal directions.
45
There are eight cardinal directions, namely: north, northeast, east, southeast, south, southwest, west, and northwest. The angle between two adjacent cardinal directions is 45°. The angle between east and northeast is 45°.
The angle between east and west is 180°.
The angle between southeast and southwest is 90°.
5. Determining the Rotating Angle
a. Angle of one revolution The angle of one revolution is 360°.
If point A is rotated with center O by 360°, it will return to point A again
b. Angle ¼ Turn Angle ¼ turn has a magnitude of 360° : 4 = 90°. Rotation from A to B with the center of rotation point O is a rotation of 90°.
c. Angle of ½ Rotation An angle of half rotation is 360° : 2 = 180°. Rotation from A to B with the center of rotation point O is a rotation of 180°.
d. Angle ¾ Turn Angle ¾ turn measures 360° : ¾ = 270°. Rotation from A to B with the center of rotation point O is a rotation of 270°.
6. Rotation / Rotation on Plane Shape
Take a look at the ABCD square below! If square ABCD is rotated ¼ turn clockwise with center O, then:
a. point A occupies point D
b. point B occupies point A
c. point C occupies point B d. point D occupies point C
7. Rotation on the Clockwork
The face of the clock is divided into 12 parts. Each section measures 30°.
The short hand every hour rotates by 30°.
The hour hand rotates 360° every hour.
The long hand rotates by 30° every 5 minutes
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