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7.2 Right Triangle Trigonometry

Sine, cosine, and tangent as side ratios, exact values at 30, 45, and 60 degrees, cofunctions, and applied height problems.

Algebra and Trigonometry 2e, 7.2 Right Triangle Trigonometry

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27 exercises

Evaluating Trigonometric Functions of Special Angles Using Side Lengths

Find the exact value of the trigonometric functions of π 3 , \frac{\pi}{3} , using side lengths.

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7.2 Exercise 6

Find the exact value of the trigonometric functions of π 4 , \frac{\pi}{4} , using side lengths.

2.5

Using Cofunction Identities

If sint= 5 12 , \sin t = \frac{5}{12} , find cos( π 2 −t ). \cos \left(\frac{\pi}{2} - t\right) .

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7.2 Exercise 8

If csc( π 6 )=2, \csc \left(\frac{\pi}{6}\right) = 2 , find sec( π 3 ). \text{sec} \left(\frac{\pi}{3}\right) .

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7.2 Exercise 10

A right triangle has one angle of π 3 \frac{\pi}{3} and a hypotenuse of 20. Find the unknown sides and angle of the triangle.

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7.2 Exercise 12

How long a ladder is needed to reach a windowsill 50 feet above the ground if the ladder rests against the building making an angle of 5π 12 \frac{5 \pi}{12} with the ground? Round to the nearest foot.

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7.2 Exercise 15

The tangent of an angle compares which sides of the right triangle?

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7.2 Exercise 17

Explain the cofunction identity.

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7.2 Exercise 19

Use cofunctions of complementary angles.

cos( π 3 )=sin( ___ ) \cos \left(\frac{\pi}{3}\right) = \sin \left(___\right)

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7.2 Exercise 21

Use cofunctions of complementary angles.

tan( π 4 )=cot( ___ ) \tan \left(\frac{\pi}{4}\right) = \cot \left(___\right)

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7.2 Exercise 23

Find the lengths of the missing sides if side a a is opposite angle A, A , side b b is opposite angle B, B , and side c c is the hypotenuse.

sinB= 1 2 ,a=20 \sin B = \frac{1}{2} , a = 20

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7.2 Exercise 25

Find the lengths of the missing sides if side a a is opposite angle A, A , side b b is opposite angle B, B , and side c c is the hypotenuse.

tanA=100,b=100 \tan A = 100 , b = 100

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7.2 Exercise 27

Find the lengths of the missing sides if side a a is opposite angle A, A , side b b is opposite angle B, B , and side c c is the hypotenuse.

a=5,∡A=60° a = 5 , \measuredangle A = 60°

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7.2 Exercise 29

sinA \sin A

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7.2 Exercise 31

tanA \tan A

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7.2 Exercise 33

secA \text{sec} A

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7.2 Exercise 35

sinA \sin A

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7.2 Exercise 37

tanA \tan A

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7.2 Exercise 39

secA \text{sec} A

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7.2 Exercise 49

Use a calculator to find the length of each side to four decimal places.

b=15,∡B=15° b = 15 , \measuredangle B = 15°

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7.2 Exercise 51

Use a calculator to find the length of each side to four decimal places.

c=50,∡B=21° c = 50 , \measuredangle B = 21°

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7.2 Exercise 53

Use a calculator to find the length of each side to four decimal places.

b=3.5,∡A=78° b = 3.5 , \measuredangle A = 78°

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7.2 Exercise 59

A radio tower is located 325 feet from a building. From a window in the building, a person determines that the angle of elevation to the top of the tower is 43°, 43° , and that the angle of depression to the bottom of the tower is 31°. 31° . How tall is the tower?

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7.2 Exercise 61

A 400-foot tall monument is located in the distance. From a window in a building, a person determines that the angle of elevation to the top of the monument is 18°, 18° , and that the angle of depression to the bottom of the monument is 3°. 3° . How far is the person from the monument?

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7.2 Exercise 63

There is lightning rod on the top of a building. From a location 500 feet from the base of the building, the angle of elevation to the top of the building is measured to be 36°. 36° . From the same location, the angle of elevation to the top of the lightning rod is measured to be 38°. 38° . Find the height of the lightning rod.

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7.2 Exercise 65

A 23-ft ladder leans against a building so that the angle between the ground and the ladder is 80°. 80° . How high does the ladder reach up the side of the building?

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7.2 Exercise 67

The angle of elevation to the top of a building in Seattle is found to be 2 degrees from the ground at a distance of 2 miles from the base of the building. Using this information, find the height of the building.

2.5

Adapted from College Algebra © 2021 Rice University. Licensed under CC BY 4.0. Sources: College Algebra 2e, Algebra and Trigonometry 2e, Precalculus 2e, College Algebra with Corequisite Support 2e. Imported at revision 4922e46.