Take note Key Concept: Types of Angles

acute angle	right angle	obtuse angle	straight angle
0 < x < 90 0 less than x less than 90	x = 90 x equals 90	90 < x < 180 90 less than x less than 180	x = 180 x equals 180

Problem 2 Measuring and Classifying Angles

What are the measures of ∠ LKN , ∠ JKL , angle  and ∠ JKN ? angle  Classify each angle as acute, right, obtuse, or straight.

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Use the definition of the measure of an angle to calculate each measure.

m ∠ LKN = | 145 − 0 | = 145 ; ∠ LKN m angle  is obtuse.

m ∠ JKL = | 90 − 145 | = | − 55 | = 55 ; ∠ JKL m angle  is acute.

m ∠ JKN = | 90 − 0 | = 90 ; ∠ JKN m angle  is right.

✓ Got It?

2. What are the measures of ∠ LKH , ∠ HKN , angle  and ∠ MKH ? angle  Classify each angle as acute, right, obtuse, or straight.