The size of an angle is usually measured in degrees (°). Think of a circle which is divided into 360 equal sectors. Each sector has a small angle at the centre of the circle – the size of such angle is 1 degree (written: 1°). In other words, the size of an angle is a measure of how wide the angle is at the vertex bound by the two sides.
Given an angle ABC ,
How do we measure the size of the angle? We can measure angles using an instrument known as a protractor.
A protractor is an instrument used to measure the size of angles.
The protractor shown below has two scales:
The outer scale starts from 0˚ to180˚ going clockwise.
The inner scale starts from 0˚ to 180˚ going anti-clockwise.
To measure angle ABC , we need to:Step 1: Place the center point of the protractor on the vertex B.
We can also adjust the base line of the protractor so that it is aligned with the line AB and use the outer scale to measure the angle.
The following videos will show you how to measure and draw angles using a protractor.Measuring and Drawing Angles
Using a Protractor
Explore how to use a protractor
Drag and drop the Protractor to measure the angle
Practice lining up and reading a protractor while you measure a set of angles in this fun learning activity. The angles may range from 0° to 180°.
Guess the Angle
Determine the acute or obtuse angle.
Rotate to landscape screen format on a mobile phone or small tablet to use the Mathway widget, a free math problem solver that answers your questions with step-by-step explanations.
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