Problem Set 45: Unit Circle: Sine and Cosine Functions

1. Describe the unit circle.
2. What do the x- and y-coordinates of the points on the unit circle represent?

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

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

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

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.

6. sin(t)<0 and cos(t)<0 7. sin(t)>0 and cos(t)>0

8. sin(t)>0 and cos(t)<0 9. sin(t)<0 and cos(t)>0

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

10. sinπ2

11. sinπ3

12. cosπ2

13. cosπ3

14. sinπ4

15. cosπ4

16. sinπ6

17. sinπ

18. sin3π2

19. cosπ

20. cos0

21. cosπ6

22. sin0

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

23. 240

24. 170

25. 100

26. 315

27. 135

28. 5π4

29. 2π3

30. 5π6

31. 11π3

32. 7π4

33. π8

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 angles on the unit circle, use a calculator and round to three decimal places.

34. 225

35. 300

36. 320

37. 135

38. 210

39. 120

40. 250

41. 150

42. 5π4

43. 7π6

44. 5π3

45. 3π4

46. 4π3

47. 2π3

48. 5π6

49. 7π4

For the following exercises, find the requested value.

50. If cos(t)=17 and t is in the 4th quadrant, find sin(t).

51. If cos(t)=29 and t is in the 1st quadrant, find sin(t).

52. If sin(t)=38 and t is in the 2nd quadrant, find cos(t).

53. If sin(t)=14 and t is in the 3rd quadrant, find cos(t).

54. Find the coordinates of the point on a circle with radius 15 corresponding to an angle of 220.

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

56. Find the coordinates of the point on a circle with radius 8 corresponding to an angle of 7π4.

57. Find the coordinates of the point on a circle with radius 16 corresponding to an angle of 5π9.

58. State the domain of the sine and cosine functions.

59. State the range of the sine and cosine functions.

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

60.
Graph of a quarter circle with angles of 0, 30, 45, 60, and 90 degrees inscribed. Equivalence of angles in radians shown. Points along circle are marked.

61.
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.

62.
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.

63.
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.

64.
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.

65.
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.

66.
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.

67.
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.

68.
Graph of circle with angle of t inscribed. Point of (1,0) is at intersection of terminal side of angle and edge of circle.

69.
Graph of circle with angle of t inscribed. Point of (-1,0) is at intersection of terminal side of angle and edge of circle.

70.
Graph of circle with angle of t inscribed. Point of (0.111,0.994) is at intersection of terminal side of angle and edge of circle.

71.
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.

72.
Graph of circle with angle of t inscribed. Point of (negative square root of 2 over 2, square root of 2 over 2) is at intersection of terminal side of angle and edge of circle.

73.
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.

74.
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.

75.
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.

76.
Graph of circle with angle of t inscribed. Point of (0, -1) is at intersection of terminal side of angle and edge of circle.

77.
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.

78.
Graph of circle with angle of t inscribed. Point of (-0.948, -0.317) is at intersection of terminal side of angle and edge of circle.

79.
Graph of circle with angle of t inscribed. Point of (0, 1) is at intersection of terminal side of angle and edge of circle.
For the following exercises, use a graphing calculator to evaluate.

80. sin5π9

81. cos5π9

82. sinπ10

83. cosπ10

84. sin3π4

85. cos3π4

86. sin98

87. cos98

88. cos310

89. sin310

Find the exact value for each of the following products.

90. sin(11π3)cos(5π6)

91. sin(3π4)cos(5π3)

92. sin(4π3)cos(π2)

93. sin(9π4)cos(π6)

94. sin(π6)cos(π3)

95. sin(7π4)cos(2π3)

96. cos(5π6)cos(2π3)

97. cos(π3)cos(π4)

98. sin(5π4)sin(11π6)

99. sin(π)sin(π6)

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.

100. What are the coordinates of the child after 45 seconds?

101. What are the coordinates of the child after 90 seconds?

102. What is the coordinates of the child after 125 seconds?

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

104. When will the child have coordinates (0.866,0.5) if the ride last 6 minutes?