Big Ideas Math Geometry, 2014
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Big Ideas Math Geometry, 2014 View details
2. Reflections
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Exercise 45 Page 188

The angle we are looking for is between the rays that start at O and pass through the points E and D.

Angle Measure: 30^(∘)
Classification: Acute

Practice makes perfect

Let's first identify the angle we are looking for. The symbol ∠ EOD refers to the angle found between the rays that start at O and pass through the points E and D.

Examining the protractor, we can see that the ray traveling through E passes through 20^(∘). Also, the ray traveling through D passes through 50^(∘). By the Protractor Postulate, the measure of ∠ EOD is the difference between 50^(∘) and 20^(∘). m ∠ EOD: 50^(∘)-20^(∘)=30^(∘) Now, we can classify the angle using its measure.

Type Measure
Acute 0^(∘)
Right m=90^(∘)
Obtuse 90^(∘)
Straight m=180^(∘)

Because our angle is 30^(∘), we know that it is acute.