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Angle Measure

Angle Measure

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Understanding the Measurement of Angles

When Emma, John's mother, was planning his birthday party, she wanted to make sure that all the guests received equal slices of cake. This required cutting the cake at equal angles. But how do we measure these angles? In this article, we will explore the concept of angle measurement in a simple and engaging manner.

An angle is formed by two rays that meet at a common point. Angle measurement involves determining the size or specific value of an angle between two rays. This can be done manually or through mathematical calculations.

Manual Measurement of Angles

A protractor is a tool that can be used to measure angles manually. Place the protractor on one of the rays, with the 0° mark at the point where the two rays intersect. Then, note the measurement where the other ray meets the protractor. This value is the measurement of the angle formed between the two rays.

For example, in the diagram above, the blue rays form an angle of 40°. Protractors measure angles in degrees.

Mathematical Measurement of Angles

Angles can also be measured mathematically using various methods. One approach is to utilize the fact that all angles on a straight line add up to 180°. This can help determine the measurement of missing angles. For instance, in the diagram below, we can find the missing angle by subtracting the known angle (109°) from 180°, resulting in an answer of 71°.

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