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In this lesson, we will learn how to use a protractor to measure angles.

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Now, this is a protractor. The point here is the 'origin'. This is the base line, the inner scale the outer scale.

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Knowing this, let's use this protractor to measure angles.

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Measure this angle, ABC. First, we place the protractor's origin, on the vertex B.

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Next, make sure that the base line is along the line BC.

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Looking at the inner scale, we can see that this angle is 70 degrees.

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Hence, the angle ABC is equals to 70 degrees.

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Next example, find the value of this angle, ABC.

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To do so, we place the protractor's origin, on the vertex B.

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Next, make sure that the base line is along the line BC.

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Now, from the inner scale, the angle is measured as, 51, 52, 53, 54, 55 degrees.

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Hence, the angle ABC is equals to, 55 degrees.

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Next example, measure the angle, ABC.

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Similarly, we place the protractor's origin on the vertex B, and make sure the base line is along the line, BC.

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From the inner scale, we can see that, this angle is 130, 131, 132 degrees.

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Hence, the angle ABC is equals to 132 degrees.

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That is all for now.

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In this lesson, we will learn on using a protractor to measure any angle that is greater than 180 degrees.

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Now, measure this angle, ABC.

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To measure this angle, we split this angle into 2 parts, by drawing a dotted line along BC.

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By finding the sum of these 2 angles, we will get the angle ABC.

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Now, we place the protractor, at the vertex B.

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Next, we rotate the protractor to that its base line is along BC.

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Here, we can see that, this angle is 180 degrees.

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Next, to measure this angle, we rotate the protractor, so that its baseline is along the line AB.

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From the outer scale, we can see that, this angle is 40 degrees.

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Hence, the angle ABC is equals to 180 degrees, plus 40 degrees.

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This gives 220 degrees. Therefore, the angle ABC is 220 degrees.

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Next example, measure this angle x using a protractor

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By now, we should know that the angle for a full rotation is 360 degrees.

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Therefore, we can find x, by taking 360 degrees, minus this angle.

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So, let’s measure this angle using a protractor.

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To do so, we place the protractor's origin, here.

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Then, make sure that the base line is along this line.

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From the outer scale, we can see that this angle is 60, 61, 62, 63, 64, 65 degrees.

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Hence, x is equals to, 360 degrees, minus by 65 degrees. This gives 295 degrees.

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That is all for this lesson, try out the practice question to further your understanding.