Every problem in the chapter beside the book’s answer, a chapter at a time as you scroll.

Chapter 5: Trigonometric Functions

226 problems · 49 figures

Try It #1 §5.1 source ↗

Show an angle of 240° on a circle in standard position.

Answer

Graph of a 240 degree angle.

Try It #2 §5.1 source ↗

Find the radian measure of three-fourths of a full rotation.

Answer

3π 2

Try It #3 §5.1 source ↗

Convert − 3π 4 radians to degrees.

Answer

−135°

Try It #4 §5.1 source ↗

Convert 126° to radians.

Answer

7π 10

Try It #5 §5.1 source ↗

Find an angle α that is coterminal with an angle measuring 870°, where 0°≤α< 360°.

Answer

α=150°

Try It #6 §5.1 source ↗

Find an angle β that is coterminal with an angle measuring −300° such that 0°≤β< 360°.

Answer

β=60°

Try It #7 §5.1 source ↗

Find an angle of measure θ that is coterminal with an angle of measure − 17π 6 where 0≤θ<2π.

Answer

7π 6

Try It #8 §5.1 source ↗

Find the arc length along a circle of radius 10 units subtended by an angle of 215°.

Answer

215π 18 = 37.525 units

Try It #9 §5.1 source ↗

In central pivot irrigation, a large irrigation pipe on wheels rotates around a center point. A farmer has a central pivot system with a radius of 400 meters. If water restrictions only allow her to water 150 thousand square meters a day, what angle should she set the system to cover? Write the answer in radian measure to two decimal places.

Answer

1.88

Try It #10 §5.1 source ↗

A vintage vinyl record is played on a turntable rotating clockwise at a rate of 45 rotations per minute. Find the angular speed in radians per second.

Answer

3π 2 rad/s

Try It #11 §5.1 source ↗

A satellite is rotating around Earth at 0.25 radians per hour at an altitude of 242 km above Earth. If the radius of Earth is 6378 kilometers, find the linear speed of the satellite in kilometers per hour.

Answer

1655 kilometers per hour

5.1-1 §5.1 source ↗

Draw an angle in standard position. Label the vertex, initial side, and terminal side.

Answer

Graph of a circle with an angle inscribed, showing the initial side, terminal side, and vertex.

5.1-3 §5.1 source ↗

State what a positive or negative angle signifies, and explain how to draw each.

Answer

Whether the angle is positive or negative determines the direction. A positive angle is drawn in the counterclockwise direction, and a negative angle is drawn in the clockwise direction.

5.1-5 §5.1 source ↗

Explain the differences between linear speed and angular speed when describing motion along a circular path.

Answer

Linear speed is a measurement found by calculating distance of an arc compared to time. Angular speed is a measurement found by calculating the angle of an arc compared to time.

5.1-7 §5.1 source ↗

For the following exercises, draw an angle in standard position with the given measure.

300°

Answer

Graph of a circle with an angle inscribed.

5.1-9 §5.1 source ↗

For the following exercises, draw an angle in standard position with the given measure.

135°

Answer

Graph of a circle with an angle inscribed.

5.1-11 §5.1 source ↗

For the following exercises, draw an angle in standard position with the given measure.

2π 3

Answer

Graph of a circle with an angle inscribed.

5.1-13 §5.1 source ↗

For the following exercises, draw an angle in standard position with the given measure.

5π 6

Answer

Graph of a circle with an angle inscribed.

5.1-15 §5.1 source ↗

For the following exercises, draw an angle in standard position with the given measure.

− π 10

Answer

Graph of a circle with an angle inscribed.

5.1-17 §5.1 source ↗

For the following exercises, draw an angle in standard position with the given measure as well as a coterminal angle.

−120°

Answer

240°

Graph of a circle with an angle inscribed.

5.1-19 §5.1 source ↗

For the following exercises, draw an angle in standard position with the given measure as well as a coterminal angle.

22π 3

Answer

4π 3

Graph of a circle showing the equivalence of two angles.

5.1-21 §5.1 source ↗

For the following exercises, draw an angle in standard position with the given measure as well as a coterminal angle.

− 4π 3

Answer

2π 3

Graph of a circle showing the equivalence of two angles.

5.1-23 §5.1 source ↗

For the following exercises, refer to Figure 25. Round to two decimal places.

Graph of a circle with radius of 3 inches and an angle of 140 degrees. Figure 25

Find the area of the sector.

Answer

7π 2 ≈ 11.00  in 2

5.1-25 §5.1 source ↗

For the following exercises, refer to Figure 26. Round to two decimal places.

Graph of a circle with angle of 2pi/5 and a radius of 4.5 cm. Figure 26

Find the area of the sector.

Answer

81π 20 ≈ 12.72  cm 2

5.1-27 §5.1 source ↗

For the following exercises, convert angles in radians to degrees.

π 9 radians

Answer

20°

5.1-29 §5.1 source ↗

For the following exercises, convert angles in radians to degrees.

π 3 radians

Answer

60°

5.1-31 §5.1 source ↗

For the following exercises, convert angles in radians to degrees.

− 5π 12 radians

Answer

−75°

5.1-33 §5.1 source ↗

For the following exercises, convert angles in degrees to radians.

90°

Answer

π 2 radians

5.1-35 §5.1 source ↗

For the following exercises, convert angles in degrees to radians.

−540°

Answer

−3π radians

5.1-37 §5.1 source ↗

For the following exercises, convert angles in degrees to radians.

180°

Answer

π radians

5.1-39 §5.1 source ↗

For the following exercises, convert angles in degrees to radians.

150°

Answer

5π 6 radians

5.1-41 §5.1 source ↗

For the following exercises, use to given information to find the length of a circular arc. Round to two decimal places.

Find the length of the arc of a circle of radius 5.02 miles subtended by the central angle of π 3 .

Answer

5.02π 3 ≈5.26 miles

5.1-43 §5.1 source ↗

For the following exercises, use to given information to find the length of a circular arc. Round to two decimal places.

Find the length of the arc of a circle of radius 10 centimeters subtended by the central angle of 50°.

Answer

25π 9 ≈8.73 centimeters

5.1-45 §5.1 source ↗

For the following exercises, use to given information to find the length of a circular arc. Round to two decimal places.

Find the length of the arc of a circle of diameter 12 meters subtended by the central angle is 63°.

Answer

21π 10 ≈6.60 meters

5.1-47 §5.1 source ↗

For the following exercises, use the given information to find the area of the sector. Round to four decimal places.

A sector of a circle has a central angle of 30° and a radius of 20 cm.

Answer

104.7198 cm2

5.1-49 §5.1 source ↗

For the following exercises, use the given information to find the area of the sector. Round to four decimal places.

A sector of a circle with radius of 0.7 inches and an angle of π radians.

Answer

0.7697 in2

5.1-51 §5.1 source ↗

For the following exercises, find the angle between 0° and 360° that is coterminal to the given angle.

−110°

Answer

250°

5.1-53 §5.1 source ↗

For the following exercises, find the angle between 0° and 360° that is coterminal to the given angle.

1400°

Answer

320°

5.1-55 §5.1 source ↗

For the following exercises, find the angle between 0 and 2π in radians that is coterminal to the given angle.

10π 3

Answer

4π 3

5.1-57 §5.1 source ↗

For the following exercises, find the angle between 0 and 2π in radians that is coterminal to the given angle.

44π 9

Answer

8π 9

5.1-59 §5.1 source ↗

For the following exercises, find the angle between 0 and 2π in radians that is coterminal to the given angle.

A bicycle with 24-inch diameter wheels is traveling at 15 mi/h. Find the angular speed of the wheels in rad/min. How many revolutions per minute do the wheels make?

Answer

1320 rad 210.085 RPM

5.1-61 §5.1 source ↗

For the following exercises, find the angle between 0 and 2π in radians that is coterminal to the given angle.

A wheel of radius 14 inches is rotating 0.5 rad/s. What is the linear speed v, the angular speed in RPM, and the angular speed in deg/s?

Answer

7 in./s, 4.77 RPM, 28.65 deg/s

5.1-63 §5.1 source ↗

For the following exercises, find the angle between 0 and 2π in radians that is coterminal to the given angle.

When being burned in a writable CD-R drive, the angular speed of a CD varies to keep the linear speed constant where the disc is being written. When writing along the outer edge of the disc, the angular speed of one drive is about 4,800 RPM (revolutions per minute. Find the linear speed if the CD has diameter of 120millimeters.

Answer

1, 809, 557.37 mm/min= 30.16 m/s

5.1-65 §5.1 source ↗

For the following exercises, find the angle between 0 and 2π in radians that is coterminal to the given angle.

Find the distance along an arc on the surface of Earth that subtends a central angle of 5 minutes ( 1 minute= 1 60  degree ) . The radius of Earth is 3960 miles.

Answer

5.76 miles

5.1-67 §5.1 source ↗

For the following exercises, find the angle between 0 and 2π in radians that is coterminal to the given angle.

Consider a clock with an hour hand and minute hand. What is the measure of the angle the minute hand traces in 20 minutes?

Answer

120°

5.1-69 §5.1 source ↗

For the following exercises, find the angle between 0 and 2π in radians that is coterminal to the given angle.

A city is located at 40 degrees north latitude. Assume the radius of the earth is 3960 miles and the earth rotates once every 24 hours. Find the linear speed of a person who resides in this city. Refer to Unit Circle: Sine and Cosine Functions for information on trigonometric functions.

Answer

794 miles per hour

5.1-71 §5.1 source ↗

For the following exercises, find the angle between 0 and 2π in radians that is coterminal to the given angle.

Find the linear speed of the moon if the average distance between the earth and moon is 239,000 miles, assuming the orbit of the moon is circular and requires about 28 days. Express answer in miles per hour.

Answer

2,234 miles per hour

5.1-73 §5.1 source ↗

For the following exercises, find the angle between 0 and 2π in radians that is coterminal to the given angle.

A car travels 3 miles. Its tires make 2640 revolutions. What is the radius of a tire in inches?

Answer

11.5 inches

Try It #1 §5.2 source ↗

A certain angle t corresponds to a point on the unit circle at ( − 2 2 , 2 2 ) as shown in Figure 5. Find cost and sint.

Graph of a circle with angle t, radius of 1, and a terminal side that intersects the circle at the point (negative square root of 2 over 2, square root of 2 over 2). Figure 5

Answer

cos(t)= − 2 2 , sin(t)= 2 2

Try It #2 §5.2 source ↗

Find cosine and sine of the angle π.

Answer

cos(π)=−1, sin(π)=0

Try It #3 §5.2 source ↗

If cos(t)= 24 25 and t is in the fourth quadrant, find sin(t).

Answer

sin(t)=− 7 25

Try It #4 §5.2 source ↗

Evaluate sin( π 3 ).

Answer

approximately 0.866025403

Try It #5 §5.2 source ↗

Find the reference angle of 5π 3 .

Answer

π 3

Try It #6 §5.2 source ↗

ⓐ Use the reference angle of 315° to find cos(315°) and sin(315°).

ⓑ Use the reference angle of − π 6 to find cos( − π 6 ) and sin( − π 6 ).

Answer

ⓐ cos(315°)= 2 2 , sin(315°)= – 2 2

ⓑ cos(− π 6 )= 3 2 , sin(− π 6 )= − 1 2

Try It #7 §5.2 source ↗

Find the coordinates of the point on the unit circle at an angle of 5π 3 .

Answer

( 1 2 ,− 3 2 )

5.2-1 §5.2 source ↗

Describe the unit circle.

Answer

The unit circle is a circle of radius 1 centered at the origin.

5.2-3 §5.2 source ↗

Discuss the difference between a coterminal angle and a reference angle.

Answer

Coterminal angles are angles that share the same terminal side. A reference angle is the size of the smallest acute angle, t, formed by the terminal side of the angle t and the horizontal axis.

5.2-5 §5.2 source ↗

Explain how the sine of an angle in the second quadrant differs from the sine of its reference angle in the unit circle.

Answer

The sine values are equal.

5.2-7 §5.2 source ↗

For the following exercises, use the given sign of the sine and cosine functions to find the quadrant in which the terminal point determined by t lies.

sin(t)>0 and cos(t)>0

Answer

I

5.2-9 §5.2 source ↗

For the following exercises, use the given sign of the sine and cosine functions to find the quadrant in which the terminal point determined by t lies.

sin(t)<0 and cos(t)>0

Answer

IV

5.2-11 §5.2 source ↗

For the following exercises, find the exact value of each trigonometric function.

sin π 3

Answer

3 2

5.2-13 §5.2 source ↗

For the following exercises, find the exact value of each trigonometric function.

cos π 3

Answer

1 2

5.2-15 §5.2 source ↗

For the following exercises, find the exact value of each trigonometric function.

cos π 4

Answer

2 2

5.2-17 §5.2 source ↗

For the following exercises, find the exact value of each trigonometric function.

sinπ

Answer

0

5.2-19 §5.2 source ↗

For the following exercises, find the exact value of each trigonometric function.

cosπ

Answer

−1

5.2-21 §5.2 source ↗

For the following exercises, find the exact value of each trigonometric function.

cos π 6

Answer

3 2

5.2-23 §5.2 source ↗

For the following exercises, state the reference angle for the given angle.

240°

Answer

60°

5.2-25 §5.2 source ↗

For the following exercises, state the reference angle for the given angle.

100°

Answer

80°

5.2-27 §5.2 source ↗

For the following exercises, state the reference angle for the given angle.

135°

Answer

45°

5.2-29 §5.2 source ↗

For the following exercises, state the reference angle for the given angle.

2π 3

Answer

π 3

5.2-31 §5.2 source ↗

For the following exercises, state the reference angle for the given angle.

−11π 3

Answer

π 3

5.2-33 §5.2 source ↗

For the following exercises, state the reference angle for the given angle.

−π 8

Answer

π 8

5.2-35 §5.2 source ↗

For the following exercises, find the reference angle, the quadrant of the terminal side, and the sine and cosine of each angle. If the angle is not one of the special angles on the unit circle, use a calculator and round to three decimal places.

300°

Answer

60°, Quadrant IV, sin(300°)= − 3 2 , cos(300°)= 1 2

5.2-37 §5.2 source ↗

For the following exercises, find the reference angle, the quadrant of the terminal side, and the sine and cosine of each angle. If the angle is not one of the special angles on the unit circle, use a calculator and round to three decimal places.

135°

Answer

45°, Quadrant II, sin(135°)= 2 2 , cos(135°)= − 2 2

5.2-39 §5.2 source ↗

For the following exercises, find the reference angle, the quadrant of the terminal side, and the sine and cosine of each angle. If the angle is not one of the special angles on the unit circle, use a calculator and round to three decimal places.

120°

Answer

60°, Quadrant II, sin(120°)= 3 2 , cos(120°)= − 1 2

5.2-41 §5.2 source ↗

For the following exercises, find the reference angle, the quadrant of the terminal side, and the sine and cosine of each angle. If the angle is not one of the special angles on the unit circle, use a calculator and round to three decimal places.

150°

Answer

30°, Quadrant II, sin(150°)= 1 2 , cos(150°)= − 3 2

5.2-43 §5.2 source ↗

For the following exercises, find the reference angle, the quadrant of the terminal side, and the sine and cosine of each angle. If the angle is not one of the special angles on the unit circle, use a calculator and round to three decimal places.

7π 6

Answer

π 6 , Quadrant III, sin( 7π 6 )= − 1 2 , cos( 7π 6 )= − 3 2

5.2-45 §5.2 source ↗

For the following exercises, find the reference angle, the quadrant of the terminal side, and the sine and cosine of each angle. If the angle is not one of the special angles on the unit circle, use a calculator and round to three decimal places.

3π 4

Answer

π 4 , Quadrant II, sin( 3π 4 )= 2 2 , cos( 3π 4 )= − 2 2

5.2-47 §5.2 source ↗

For the following exercises, find the reference angle, the quadrant of the terminal side, and the sine and cosine of each angle. If the angle is not one of the special angles on the unit circle, use a calculator and round to three decimal places.

2π 3

Answer

π 3 , Quadrant II, sin( 2π 3 )= 3 2 , cos( 2π 3 )= − 1 2

5.2-49 §5.2 source ↗

For the following exercises, find the reference angle, the quadrant of the terminal side, and the sine and cosine of each angle. If the angle is not one of the special angles on the unit circle, use a calculator and round to three decimal places.

7π 4

Answer

π 4 , Quadrant IV, sin( 7π 4 )= − 2 2 , cos( 7π 4 )= 2 2

5.2-51 §5.2 source ↗

For the following exercises, find the requested value.

If cos( t )= 2 9 and t is in the 1st quadrant, find sin(t).

Answer

77 9

5.2-53 §5.2 source ↗

For the following exercises, find the requested value.

If sin( t )=− 1 4 and t is in the 3rd quadrant, find cos(t).

Answer

− 15 4

5.2-55 §5.2 source ↗

For the following exercises, find the requested value.

Find the coordinates of the point on a circle with radius 20 corresponding to an angle of 120°.

Answer

( −10,10 3 )

5.2-57 §5.2 source ↗

For the following exercises, find the requested value.

Find the coordinates of the point on a circle with radius 16 corresponding to an angle of 5π 9 .

Answer

( –2.778,15.757 )

5.2-59 §5.2 source ↗

For the following exercises, find the requested value.

State the range of the sine and cosine functions.

Answer

[ –1,1 ]

5.2-61 §5.2 source ↗

For the following exercises, use the given point on the unit circle to find the value of the sine and cosine of t.

Graph of circle with angle of t inscribed. Point of (negative square root of 3 over 2, 1/2) is at intersection of terminal side of angle and edge of circle.

Answer

sint= 1 2, cost= − 3 2

5.2-63 §5.2 source ↗

For the following exercises, use the given point on the unit circle to find the value of the sine and cosine of t.

Graph of circle with angle of t inscribed. Point of (negative square root of 2 over 2, negative square root of 2 over 2) is at intersection of terminal side of angle and edge of circle.

Answer

sint= − 2 2 , cost= − 2 2

5.2-65 §5.2 source ↗

For the following exercises, use the given point on the unit circle to find the value of the sine and cosine of t.

Graph of circle with angle of t inscribed. Point of (-1/2, square root of 3 over 2) is at intersection of terminal side of angle and edge of circle.

Answer

sint= 3 2 , cost= − 1 2

5.2-67 §5.2 source ↗

For the following exercises, use the given point on the unit circle to find the value of the sine and cosine of t.

Graph of circle with angle of t inscribed. Point of (square root of 2 over 2, negative square root of 2 over 2) is at intersection of terminal side of angle and edge of circle.

Answer

sint= − 2 2 , cost= 2 2

5.2-69 §5.2 source ↗

For the following exercises, use the given point on the unit circle to find the value of the sine and cosine of t.

Graph of circle with angle of t inscribed. Point of (-1,0) is at intersection of terminal side of angle and edge of circle.

Answer

sint= 0, cost= − 1

5.2-71 §5.2 source ↗

For the following exercises, use the given point on the unit circle to find the value of the sine and cosine of t.

Graph of circle with angle of t inscribed. Point of (0.803,-0.596 is at intersection of terminal side of angle and edge of circle.

Answer

sint= − 0.596, cost= 0.803

5.2-73 §5.2 source ↗

For the following exercises, use the given point on the unit circle to find the value of the sine and cosine of t.

Graph of circle with angle of t inscribed. Point of (square root of 3 over 2, 1/2) is at intersection of terminal side of angle and edge of circle.

Answer

sint= 1 2 , cost= 3 2

5.2-75 §5.2 source ↗

For the following exercises, use the given point on the unit circle to find the value of the sine and cosine of t.

Graph of circle with angle of t inscribed. Point of (square root of 3 over 2, -1/2) is at intersection of terminal side of angle and edge of circle.

Answer

sint= − 1 2 , cost= 3 2

5.2-77 §5.2 source ↗

For the following exercises, use the given point on the unit circle to find the value of the sine and cosine of t.

Graph of circle with angle of t inscribed. Point of (-0.649, 0.761) is at intersection of terminal side of angle and edge of circle.

Answer

sint= 0.761, cost= − 0.649

5.2-79 §5.2 source ↗

For the following exercises, use the given point on the unit circle to find the value of the sine and cosine of t.

Graph of circle with angle of t inscribed. Point of (0, 1) is at intersection of terminal side of angle and edge of circle.

Answer

sint= 1, cost= 0

5.2-81 §5.2 source ↗

For the following exercises, use a graphing calculator to evaluate.

cos 5π 9

Answer

−0.1736

5.2-83 §5.2 source ↗

For the following exercises, use a graphing calculator to evaluate.

cos π 10

Answer

0.9511

5.2-85 §5.2 source ↗

For the following exercises, use a graphing calculator to evaluate.

cos 3π 4

Answer

−0.7071

5.2-87 §5.2 source ↗

For the following exercises, use a graphing calculator to evaluate.

cos98°

Answer

−0.1392

5.2-89 §5.2 source ↗

For the following exercises, use a graphing calculator to evaluate.

sin310°

Answer

−0.7660

5.2-91 §5.2 source ↗

For the following exercises, evaluate.

sin( 3π 4 )cos( 5π 3 )

Answer

2 4

5.2-93 §5.2 source ↗

For the following exercises, evaluate.

sin( −9π 4 )cos( −π 6 )

Answer

− 6 4

5.2-95 §5.2 source ↗

For the following exercises, evaluate.

sin( 7π 4 )cos( −2π 3 )

Answer

2 4

5.2-97 §5.2 source ↗

For the following exercises, evaluate.

cos( −π 3 )cos( π 4 )

Answer

2 4

5.2-99 §5.2 source ↗

For the following exercises, evaluate.

sin( π )sin( π 6 )

Answer

0

5.2-101 §5.2 source ↗

For the following exercises, use this scenario: A child enters a carousel that takes one minute to revolve once around. The child enters at the point ( 0,1 ), that is, on the due north position. Assume the carousel revolves counter clockwise.

What are the coordinates of the child after 90 seconds?

Answer

( 0,–1 )

5.2-103 §5.2 source ↗

For the following exercises, use this scenario: A child enters a carousel that takes one minute to revolve once around. The child enters at the point ( 0,1 ), that is, on the due north position. Assume the carousel revolves counter clockwise.

When will the child have coordinates ( 0.707,–0.707 ) if the ride lasts 6 minutes? (There are multiple answers.)

Answer

37.5 seconds, 97.5 seconds, 157.5 seconds, 217.5 seconds, 277.5 seconds, 337.5 seconds

Try It #1 §5.3 source ↗

The point ( 2 2 ,− 2 2 ) is on the unit circle, as shown in Figure 3. Find sint, cost, tant, sect, csct, and cott.

Graph of circle with angle of t inscribed. Point of (square root of 2 over 2, negative square root of 2 over 2) is at intersection of terminal side of angle and edge of circle. Figure 3

Answer

sint=− 2 2 , cost= 2 2 , tant=−1, sect= 2 , csct=− 2 , cott=−1

Try It #2 §5.3 source ↗

Find sint, cost, tant, sect, csct, and cott when t= π 3 .

Answer

sin π 3 = 3 2 , cos π 3 = 1 2 , tan π 3 = 3 , sec π 3 =2, csc π 3 = 2 3 3 , cot π 3 = 3 3

Try It #3 §5.3 source ↗

Use reference angles to find all six trigonometric functions of − 7π 4 .

Answer

sin( −7π 4 )= 2 2 , cos( −7π 4 )= 2 2 , tan( −7π 4 )= 1,
sec( −7π 4 )= 2 , csc( −7π 4 )= 2 , cot( −7π 4 )= 1

Try It #4 §5.3 source ↗

If the cotangent of angle t is 3 , what is the cotangent of −t?

Answer

− 3

Try It #5 §5.3 source ↗

Evaluate csc( 7π 6 ).

Answer

−2

Try It #6 §5.3 source ↗

Simplify (tant)(cost).

Answer

sint

Try It #7 §5.3 source ↗

If sec(t)=− 17 8 and 0< t< π, find the values of the other five functions.

Answer

cost= − 8 17 , sint= 15 17 , tant= − 15 8
csct= 17 15 , cott= − 8 15

Try It #8 §5.3 source ↗

Find the values of the six trigonometric functions of angle t based on Figure 10.

Graph of circle with angle of t inscribed. Point of (0, -1) is at intersection of terminal side of angle and edge of circle. Figure 10

Answer

sint=−1,cost=0,tant=Undefined sect= Undefined,csct=−1,cott=0

Try It #9 §5.3 source ↗

If sin( t )= 2 2 and cos( t )= 2 2 , find sec(t), csc(t), tan(t),  and cot(t).

Answer

sect= 2 , csct= 2 , tant= 1, cott= 1

Try It #10 §5.3 source ↗

Evaluate the cotangent of − π 8 .

Answer

≈−2.414

5.3-1 §5.3 source ↗

On an interval of [ 0,2π ), can the sine and cosine values of a radian measure ever be equal? If so, where?

Answer

Yes, when the reference angle is π 4 and the terminal side of the angle is in quadrants I and III. Thus, at x= π 4 , 5π 4 , the sine and cosine values are equal.

5.3-3 §5.3 source ↗

For any angle in quadrant II, if you knew the sine of the angle, how could you determine the cosine of the angle?

Answer

Substitute the sine of the angle in for y in the Pythagorean Theorem x 2 + y 2 =1. Solve for x and take the negative solution.

5.3-5 §5.3 source ↗

Tangent and cotangent have a period of π. What does this tell us about the output of these functions?

Answer

The outputs of tangent and cotangent will repeat every π units.

5.3-7 §5.3 source ↗

For the following exercises, find the exact value of each expression.

sec π 6

Answer

2 3 3

5.3-9 §5.3 source ↗

For the following exercises, find the exact value of each expression.

cot π 6

Answer

3

5.3-11 §5.3 source ↗

For the following exercises, find the exact value of each expression.

sec π 4

Answer

2

5.3-13 §5.3 source ↗

For the following exercises, find the exact value of each expression.

cot π 4

Answer

1

5.3-15 §5.3 source ↗

For the following exercises, find the exact value of each expression.

sec π 3

Answer

2

5.3-17 §5.3 source ↗

For the following exercises, find the exact value of each expression.

cot π 3

Answer

3 3

5.3-19 §5.3 source ↗

For the following exercises, use reference angles to evaluate the expression.

sec 7π 6

Answer

− 2 3 3

5.3-21 §5.3 source ↗

For the following exercises, use reference angles to evaluate the expression.

cot 13π 6

Answer

3

5.3-23 §5.3 source ↗

For the following exercises, use reference angles to evaluate the expression.

sec 3π 4

Answer

− 2

5.3-25 §5.3 source ↗

For the following exercises, use reference angles to evaluate the expression.

cot 11π 4

Answer

−1

5.3-27 §5.3 source ↗

For the following exercises, use reference angles to evaluate the expression.

sec 4π 3

Answer

−2

5.3-29 §5.3 source ↗

For the following exercises, use reference angles to evaluate the expression.

cot 5π 3

Answer

− 3 3

5.3-31 §5.3 source ↗

For the following exercises, use reference angles to evaluate the expression.

sec300°

Answer

2

5.3-33 §5.3 source ↗

For the following exercises, use reference angles to evaluate the expression.

cot240°

Answer

3 3

5.3-35 §5.3 source ↗

For the following exercises, use reference angles to evaluate the expression.

sec120°

Answer

−2

5.3-37 §5.3 source ↗

For the following exercises, use reference angles to evaluate the expression.

cot315°

Answer

−1

5.3-39 §5.3 source ↗

For the following exercises, use reference angles to evaluate the expression.

If cost=− 1 3 , and t is in quadrant III, find sint, sect, csct, tant, cott.

Answer

If sint=− 2 2 3 , sect=−3, csct=− 3 2 4 , tant=2 2 , cott= 2 4

5.3-41 §5.3 source ↗

For the following exercises, use reference angles to evaluate the expression.

If sint= 3 2 and cost= 1 2 , find sect, csct, tant, and cott.

Answer

sect=2, csct= 2 3 3 , tant= 3 , cott= 3 3

5.3-43 §5.3 source ↗

For the following exercises, use reference angles to evaluate the expression.

If sint= 2 2 , what is the sin(−t)?

Answer

− 2 2

5.3-45 §5.3 source ↗

For the following exercises, use reference angles to evaluate the expression.

If sect=3.1, what is the sec(−t)?

Answer

3.1

5.3-47 §5.3 source ↗

For the following exercises, use reference angles to evaluate the expression.

If tant=−1.4, what is the tan(−t)?

Answer

1.4

5.3-49 §5.3 source ↗

For the following exercises, use the angle in the unit circle to find the value of the each of the six trigonometric functions.

Graph of circle with angle of t inscribed. Point of (square root of 2 over 2, square root of 2 over 2) is at intersection of terminal side of angle and edge of circle.

Answer

sint= 2 2 , cost= 2 2 , tant= 1, cott= 1, sect= 2 , csct= 2

5.3-51 §5.3 source ↗

For the following exercises, use the angle in the unit circle to find the value of the each of the six trigonometric functions.

Graph of circle with angle of t inscribed. Point of (-1/2, negative square root of 3 over 2) is at intersection of terminal side of angle and edge of circle.

Answer

sint=− 3 2 , cost=− 1 2 , tant= 3 , cott= 3 3 , sect=−2, csct=− 2 3 3

5.3-53 §5.3 source ↗

For the following exercises, use a graphing calculator to evaluate.

cot 4π 7

Answer

–0.228

5.3-55 §5.3 source ↗

For the following exercises, use a graphing calculator to evaluate.

tan 5π 8

Answer

–2.414

5.3-57 §5.3 source ↗

For the following exercises, use a graphing calculator to evaluate.

csc π 4

Answer

1.414

5.3-59 §5.3 source ↗

For the following exercises, use a graphing calculator to evaluate.

cot33°

Answer

1.540

5.3-61 §5.3 source ↗

For the following exercises, use a graphing calculator to evaluate.

sec310°

Answer

1.556

5.3-63 §5.3 source ↗

For the following exercises, use identities to evaluate the expression.

If tan( t )≈1.3, and cos(t)≈ 0.61, find sin( t ).

Answer

sin( t )≈0.79

5.3-65 §5.3 source ↗

For the following exercises, use identities to evaluate the expression.

If cot(t)≈ 0.58, and cos( t )≈0.5, find csc( t ).

Answer

csct≈1.16

5.3-67 §5.3 source ↗

For the following exercises, use identities to evaluate the expression.

Determine whether the function f(x)= 3 sin 2 xcosx+ secx is even, odd, or neither.

Answer

even

5.3-69 §5.3 source ↗

For the following exercises, use identities to evaluate the expression.

Determine whether the function f(x)= csc 2 x+ secx is even, odd, or neither.

Answer

even

5.3-71 §5.3 source ↗

For the following exercises, use identities to simplify the expression.

sect csct

Answer

sint cost = tant

5.3-73 §5.3 source ↗

For the following exercises, use identities to simplify the expression.

The amount of sunlight in a certain city can be modeled by the function h= 16cos( 1 500 d), where h represents the hours of sunlight, and d is the day of the year. Use the equation to find how many hours of sunlight there are on September 24, the 267th day of the year. State the period of the function.

Answer

13.77 hours, period: 1000π

5.3-75 §5.3 source ↗

For the following exercises, use identities to simplify the expression.

The height of a piston, h, in inches, can be modeled by the equation y=2cosx+6, where x represents the crank angle. Find the height of the piston when the crank angle is 30°.

Answer

7.73 inches

Try It #1 §5.4 source ↗

Given the triangle shown in Figure 4, find the value of sint.

A right triangle with sides of 7, 24, and 25. Also labeled is angle t. Figure 4

Answer

7 25

Try It #2 §5.4 source ↗

Using the triangle shown in Figure 7, evaluate sint, cost, tant, sect, csct, and cott.

Right triangle with sides 33, 56, and 65. Angle t is also labeled. Figure 7

Answer

sint= 33 65 ,cost= 56 65 ,tant= 33 56 , sect= 65 56 ,csct= 65 33 ,cott= 56 33

Try It #3 §5.4 source ↗

Find the exact value of the trigonometric functions of π 4 , using side lengths.

Answer

sin( π 4 )= 1 2 , cos( π 4 )= 1 2 , tan( π 4 )= 1,
sec( π 4 )= 2 , csc( π 4 )= 2 , cot( π 4 )= 1

Try It #4 §5.4 source ↗

If csc( π 6 )=2, find sec( π 3 ).

Answer

2

Try It #5 §5.4 source ↗

A right triangle has one angle of π 3 and a hypotenuse of 20. Find the unknown sides and angle of the triangle.

Answer

adjacent= 10; opposite= 10 3 ; missing angle is π 6

Try It #6 §5.4 source ↗

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 with the ground? Round to the nearest foot.

Answer

About 52 ft

5.4-1 §5.4 source ↗

For the given right triangle, label the adjacent side, opposite side, and hypotenuse for the indicated angle.

A right triangle.

Answer

A right triangle with side opposite, adjacent, and hypotenuse labeled.

5.4-3 §5.4 source ↗

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

Answer

The tangent of an angle is the ratio of the opposite side to the adjacent side.

5.4-5 §5.4 source ↗

Explain the cofunction identity.

Answer

For example, the sine of an angle is equal to the cosine of its complement; the cosine of an angle is equal to the sine of its complement.

5.4-7 §5.4 source ↗

For the following exercises, use cofunctions of complementary angles.

cos( π 3 )= sin(___)

Answer

π 6

5.4-9 §5.4 source ↗

For the following exercises, use cofunctions of complementary angles.

tan( π 4 )= cot(__)

Answer

π 4

5.4-11 §5.4 source ↗

For the following exercises, find the lengths of the missing sides if side a is opposite angle A, side b is opposite angle B, and side c is the hypotenuse.

sinB= 1 2 , a= 20

Answer

b= 20 3 3 , c= 40 3 3

5.4-13 §5.4 source ↗

For the following exercises, find the lengths of the missing sides if side a is opposite angle A, side b is opposite angle B, and side c is the hypotenuse.

tanA= 100, b= 100

Answer

a= 10, 000, c= 10, 000.5

5.4-15 §5.4 source ↗

For the following exercises, find the lengths of the missing sides if side a is opposite angle A, side b is opposite angle B, and side c is the hypotenuse.

a=5,∡A= 60 ∘

Answer

b= 5 3 3 , c= 10 3 3

5.4-17 §5.4 source ↗

For the following exercises, use Figure 14 to evaluate each trigonometric function of angle A.

A right triangle with sides 4 and 10 and angle of A labeled. Figure 14

sinA

Answer

5 29 29

5.4-19 §5.4 source ↗

For the following exercises, use Figure 14 to evaluate each trigonometric function of angle A.

A right triangle with sides 4 and 10 and angle of A labeled. Figure 14

tanA

Answer

5 2

5.4-21 §5.4 source ↗

For the following exercises, use Figure 14 to evaluate each trigonometric function of angle A.

A right triangle with sides 4 and 10 and angle of A labeled. Figure 14

secA

Answer

29 2

5.4-23 §5.4 source ↗

For the following exercises, use Figure 15 to evaluate each trigonometric function of angle A.

A right triangle with sides of 10 and 8 and angle of A labeled. Figure 15

sinA

Answer

5 41 41

5.4-25 §5.4 source ↗

For the following exercises, use Figure 15 to evaluate each trigonometric function of angle A.

A right triangle with sides of 10 and 8 and angle of A labeled. Figure 15

tanA

Answer

5 4

5.4-27 §5.4 source ↗

For the following exercises, use Figure 15 to evaluate each trigonometric function of angle A.

A right triangle with sides of 10 and 8 and angle of A labeled. Figure 15

secA

Answer

41 4

5.4-29 §5.4 source ↗

For the following exercises, solve for the unknown sides of the given triangle.

A right triangle with sides of 7, b, and c labeled. Angles of B and 30 degrees also labeled.

Answer

c=14,b=7 3

5.4-31 §5.4 source ↗

For the following exercises, solve for the unknown sides of the given triangle.

A right triangle with corners labeled A, B, and C. Hypotenuse has length of 15 times square root of 2. Angle B is 45 degrees.

Answer

a=15,b=15

5.4-33 §5.4 source ↗

For the following exercises, use a calculator to find the length of each side to four decimal places.

A right triangle with sides of 7, b, and c. Angles of 35 degrees and B are also labeled.

Answer

b= 9.9970, c= 12.2041

5.4-35 §5.4 source ↗

For the following exercises, use a calculator to find the length of each side to four decimal places.

A right triangle with sides a, b, and 12. Angles of 10 degrees and B are also labeled.

Answer

a= 2.0838, b= 11.8177

5.4-37 §5.4 source ↗

For the following exercises, use a calculator to find the length of each side to four decimal places.

b=15,∡B= 15 ∘

Answer

a= 55.9808, c= 57.9555

5.4-39 §5.4 source ↗

For the following exercises, use a calculator to find the length of each side to four decimal places.

c=50,∡B= 21 ∘

Answer

a= 46.6790, b= 17.9184

5.4-41 §5.4 source ↗

For the following exercises, use a calculator to find the length of each side to four decimal places.

b= 3.5, ∡A= 78 ∘

Answer

a= 16.4662, c= 16.8341

5.4-43 §5.4 source ↗

For the following exercises, use a calculator to find the length of each side to four decimal places.

Find x.

A triangle with angles of 36 degrees and 50 degrees and side x. Bisector in triangle with length of 85.

Answer

188.3159

5.4-45 §5.4 source ↗

For the following exercises, use a calculator to find the length of each side to four decimal places.

Find x.

A right triangle with side of 119 and angle of 26 degrees. Within right triangle there is another right triangle with angle of 70 degrees instead of 26 degrees. Difference in side length between two triangles is x.

Answer

200.6737

5.4-47 §5.4 source ↗

For the following exercises, use a calculator to find the length of each side to four decimal places.

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°, and that the angle of depression to the bottom of the tower is 31°. How tall is the tower?

Answer

498.3471 ft

5.4-49 §5.4 source ↗

For the following exercises, use a calculator to find the length of each side to four decimal places.

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°, and that the angle of depression to the bottom of the monument is 3°. How far is the person from the monument?

Answer

1060.09 ft

5.4-51 §5.4 source ↗

For the following exercises, use a calculator to find the length of each side to four decimal places.

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°. From the same location, the angle of elevation to the top of the lightning rod is measured to be 38°. Find the height of the lightning rod.

Answer

27.372 ft

5.4-53 §5.4 source ↗

For the following exercises, use a calculator to find the length of each side to four decimal places.

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

Answer

22.6506 ft

5.4-55 §5.4 source ↗

For the following exercises, use a calculator to find the length of each side to four decimal places.

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.

Answer

368.7633 ft

5.R-1 §5.R source ↗

For the following exercises, convert the angle measures to degrees.

π 4

Answer

45°

5.R-3 §5.R source ↗

For the following exercises, convert the angle measures to radians.

-210°

Answer

− 7π 6

5.R-5 §5.R source ↗

For the following exercises, convert the angle measures to radians.

Find the length of an arc in a circle of radius 7 meters subtended by the central angle of 85°.

Answer

10.385 meters

5.R-7 §5.R source ↗

For the following exercises, find the angle between 0° and 360° that is coterminal with the given angle.

420°

Answer

60°

5.R-9 §5.R source ↗

For the following exercises, find the angle between 0 and 2π in radians that is coterminal with the given angle.

− 20π 11

Answer

2π 11

5.R-11 §5.R source ↗

For the following exercises, draw the angle provided in standard position on the Cartesian plane.

-210°

Answer

A graph of a circle with a negative angle inscribed.

5.R-13 §5.R source ↗

For the following exercises, draw the angle provided in standard position on the Cartesian plane.

5π 4

Answer

A graph of a circle with an angle inscribed.

5.R-15 §5.R source ↗

For the following exercises, draw the angle provided in standard position on the Cartesian plane.

Find the linear speed of a point on the equator of the earth if the earth has a radius of 3,960 miles and the earth rotates on its axis every 24 hours. Express answer in miles per hour.

Answer

1036.73 miles per hour

5.R-17 §5.R source ↗

For the following exercises, draw the angle provided in standard position on the Cartesian plane.

Find the exact value of sin π 3 .

Answer

3 2

5.R-19 §5.R source ↗

For the following exercises, draw the angle provided in standard position on the Cartesian plane.

Find the exact value of cosπ.

Answer

–1

5.R-21 §5.R source ↗

For the following exercises, draw the angle provided in standard position on the Cartesian plane.

State the reference angle for 3π 4 .

Answer

π 4

5.R-23 §5.R source ↗

For the following exercises, draw the angle provided in standard position on the Cartesian plane.

Compute sine of 5π 4 .

Answer

− 2 2

5.R-25 §5.R source ↗

For the following exercises, draw the angle provided in standard position on the Cartesian plane.

State the range of the sine and cosine functions.

Answer

[ –1,1 ]

5.R-27 §5.R source ↗

For the following exercises, find the exact value of the given expression.

tan π 4

Answer

1

5.R-29 §5.R source ↗

For the following exercises, find the exact value of the given expression.

sec π 4

Answer

2

5.R-31 §5.R source ↗

For the following exercises, use reference angles to evaluate the given expression.

sec315°

Answer

2

5.R-33 §5.R source ↗

For the following exercises, use reference angles to evaluate the given expression.

If tan(t)= − 0.6, what is the tan(−t)?

Answer

0.6

5.R-35 §5.R source ↗

For the following exercises, use reference angles to evaluate the given expression.

If cos(t)= 2 2 , find sin(t+2π). There are two possible solutions.

Answer

2 2 or − 2 2

5.R-37 §5.R source ↗

For the following exercises, use reference angles to evaluate the given expression.

Which trigonometric functions are odd?

Answer

sine, cosecant, tangent, cotangent

5.R-39 §5.R source ↗

For the following exercises, use side lengths to evaluate.

cot π 3

Answer

3 3

5.R-41 §5.R source ↗

For the following exercises, use side lengths to evaluate.

cos( π 2 )= sin(__°)

Answer

0

5.R-43 §5.R source ↗

For the following exercises, use the given information to find the lengths of the other two sides of the right triangle.

cosB= 3 5 ,a=6

Answer

b=8,c=10

5.R-45 §5.R source ↗

For the following exercises, use Figure 1 to evaluate each trigonometric function.

A right triangle with side lengths of 11 and 6. Corners A and B are also labeled. Figure 1

sinA

Answer

11 157 157

5.R-47 §5.R source ↗

For the following exercises, solve for the unknown sides of the given triangle.

A right triangle with corners labeled A, B, and C. Hyptenuse has length of 4 times square root of 2. Other angles measure 45 degrees.

Answer

a=4,b=4

5.R-49 §5.R source ↗

For the following exercises, solve for the unknown sides of the given triangle.

A 15-ft ladder leans against a building so that the angle between the ground and the ladder is 70°. How high does the ladder reach up the side of the building?

Answer

14.0954 ft

5.T-1 §5.T source ↗

Convert 5π 6 radians to degrees.

Answer

150°

5.T-3 §5.T source ↗

Find the length of a circular arc with a radius 12 centimeters subtended by the central angle of 30°.

Answer

6.283 centimeters

5.T-5 §5.T source ↗

Find the angle between 0° and 360° that is coterminal with 375°.

Answer

15°

5.T-7 §5.T source ↗

Draw the angle 315° in standard position on the Cartesian plane.

Answer

A graph of a circle with an angle inscribed.

5.T-9 §5.T source ↗

A carnival has a Ferris wheel with a diameter of 80 feet. The time for the Ferris wheel to make one revolution is 75 seconds. What is the linear speed in feet per second of a point on the Ferris wheel? What is the angular speed in radians per second?

Answer

3.351 feet per second, 2π 75 radians per second

5.T-11 §5.T source ↗

Compute sine of 240°.

Answer

− 3 2

5.T-13 §5.T source ↗

State the range of the sine and cosine functions.

Answer

[ –1,1 ]

5.T-15 §5.T source ↗

Find the exact value of tan π 3 .

Answer

3

5.T-17 §5.T source ↗

Use reference angles to evaluate tan210°.

Answer

3 3

5.T-19 §5.T source ↗

If cost= 3 2 , find cos(t−2π).

Answer

3 2

5.T-21 §5.T source ↗

Find the missing angle: cos( π 6 )= sin(___)

Answer

π 3

5.T-23 §5.T source ↗

Find the missing sides of the triangle.

A right triangle with hyptenuse length of 9 and angle measure of 60 degrees.

Answer

a= 9 2 ,b= 9 3 2

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Problems and answers are adapted from Precalculus 2e by Jay Abramson, OpenStax, and are used under the CC BY-NC-SA 4.0 licence. Access for free at https://openstax.org/books/precalculus-2e/pages/1-introduction-to-functions. Illustrations: Copyright Rice University, OpenStax, under CC BY-NC-SA 4.0 license. This adaptation is released under the same licence, is non-commercial, and is neither affiliated with nor endorsed by OpenStax or Rice University.