Back to: Mathematics Primary 6
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Angles are very important in our daily life so it’s very necessary to understand angles.
Two rays meeting at a common endpoint form an angle.
In the adjoining figure, two rays AB and BC are called the arms of the angle ABC.
Common endpoint B is called the vertex of the angle. We can name the angle as ∠ABC, ∠B or ∠1. The symbol for denoting an angle is ∠.
The size of the angles above is 30o and 45o.
Clock faces can be used to denote angles.
Note: sum of angles of a point is 360°, therefore between one hour and another hour is 30°, it between two hours is 60°, and so on. One minute is 60°. E.g. draw a 120° on a clock.
Measuring Angles
We measure the size of an angle by using protractor. The protractor is in the shape of a semicircle. The semicircle is divided into 180 equal parts which show angle measurements from 0° to 180°.
For Example:
- Use your protractor to draw 60°.
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Using your protractor, measure and draw 30o, 45o, 90o and 120o.
Angles in A Triangle
The three interior angles in a triangle will always add up to 180°
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