707 7.3 Sum and Difference Identities Find the exact value of each expression. See Example 1. 11. cos 75° 12. cos1-15°2 13. cos1-105°2 1Hint: -105° = -60° + 1-45°22 14. cos 105° (Hint: 105° = 60° + 45°) 15. cos 7p 12 16. cos p 12 17. cos ap 12b 18. cos a7p 12b 19. cos 40° cos 50° - sin40° sin50° 20. cos 7p 9 cos 2p 9 - sin 7p 9 sin 2p 9 Write each function value in terms of the cofunction of a complementary angle. See Example 2. 21. tan87° 22. sin15° 23. cos p 12 24. sin 2p 5 25. csc 14° 24′ 26. sin142° 14′ 27. sin 5p 8 28. cot 9p 10 Use identities to fill in each blank with the appropriate trigonometric function name. See Example 2. 29. cot p 3 = ________ p 6 30. sin 2p 3 = ________ ap 6b 31. _____33° = sin57° 32. ________ 72° = cot 18° 33. cos 70° = 1 20° 34. tan24° = 1 66° Find one value of u or x that satisfies each of the following. See Example 2. 35. tanu = cot145° + 2u2 36. sinu = cos12u + 30°2 37. sec x = csc 2p 3 38. cos x = sin p 12 39. sin13u - 15°2 = cos1u + 25°2 40. cot1u - 10°2 = tan12u - 20°2 Find the exact value of each expression. See Example 3. 41. sin165° 42. sin255° 43. tan165° 44. tan285° 45. sin 5p 12 46. sin 13p 12 47. tan p 12 48. tan 5p 12 49. sin 7p 12 50. sin p 12 51. sina7p 12 b 52. sina5p 12b 53. tana5p 12 b 54. tana7p 12 b 55. tan 11p 12 56. sina13p 12 b 57. sin76° cos 31° - cos 76° sin31° 58. sin40° cos 50° + cos 40° sin50° 59. sin p 5 cos 3p 10 + cos p 5 sin 3p 10 60. sin 5p 9 cos p 18 - cos 5p 9 sin p 18 61. tan80° + tan55° 1 - tan80° tan55° 62. tan80° - tan1-55°2 1 + tan80° tan1-55°2
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