25. cos 165°

Algebra & Trigonometry with Analytic Geometry
13th Edition
ISBN:9781133382119
Author:Swokowski
Publisher:Swokowski
Chapter7: Analytic Trigonometry
Section7.4: Multiple-angle Formulas
Problem 67E
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25,31 plz
ION 7.6 Double-angle and Half-angle Formulas 507
7.6 Assess Your Understanding
2V5
Concepts and Vocabulary
7. Multiple Choice Choose the expression that completes the
Half-angle Formula for cosine functions: cos
1. cos (20) = cos 0
1-cos 0
cos a
1+ cos a
2. sin
(a) t
(b) +
2
(d)
1 cos 0
cos a
sin a
1- cos a
3. tan5
(c) +
(d) +
V1 + cos a
contain + and-
2 tan 0
4. True or False tan (20) =
1
tan e
cos 0
then which
8. Multiple Choice If sin a = ±.
s True or False sin (20) has two equivalent forms:
2 sin e cos 0 and sin? 0 - cos? A
( True or False tan (20) + tan (20) = tan(40)
ormulas
statement describes how e is related to a?
(a) 0 = a
(b) 0 =
(c) 0 = 2a (d) 0 = a?
Formula (9)
Skill Building
Problems 9-20, use the information given about the angle 0, 0se < 27, to find the exact value of:
(a) sin (20)
(b) cos (20)
(c) sin
(d) cos
Double-angle Form
3
3
10. cos 0 =
5'
4
11. tan 0 =
TT
0 < 0 <
5'
>0 > 0
< 0 <T
3' T <0 <
V3 37
3' 2
9. sin 0 =
2
37
12. tan 0 =
2'
1
T <0 <
13. cos e = -
e < 27
14. sin 0 =
3' 2
in
16. csc e =
- V5, cos e < 0
17. cot 0 = -2, sec 0 < 0
15. sec 0 = 3, sin 0 > 0
19. tan 0 = -3, sin e < 0
20. cot 0 = 3, cos 0 < 0
18. sec 0 = 2, csc 0 < 0
tan
In Problems 21-30, use Half-angle Formulas to find the exact value of each expression.
\21. sin 22.5°
22. cos 22.5°
23. tan
8
24. tan
8
157
27. sec
8
7
28. csc
8
26. sin 195°
25. cos 165°
37
30. cos
29. sin
In Problems 31-42, f(x) = sin x, g(x) = cos x, and h(x) = tan x. Use the figures below to evaluate each function.
y
31. f(20)
32. g(20)
x2 + y2 = 5
x2 + y2 = 1
(х, 2)
3A.
33. gl
35. h(20)
36.
nogab0 ne lo a o
38. f(2u) a T ()
37. g(2a)
42. h(2a)
41. h
39.
40.
A slumol
tained as i
44. Show that sin (40) = (cos 0) (4 sin 0 – 8 sin° 0).
3
43. Show that sin“ 0 =
8
1
cos (20) + cos (46).
1
cos (80).
3
A 46. Show that sin" 0 cos“ e =
128
1
cos (40) + 128°
1
1
32
A 45. Show that sin? 0 cos² 0
cos (40).
48. Find an expression for cos ( 40) as a fourth-degree polynomial
in the variable cos 0.
8
4%. Find an expression for cos ( 30) as a third-degree polynomial
in the variable cos 0.
49. Find an expression for sin ( 50) as a fifth-degree polynomial
in the variable sin 0.
50. Find an expression for cos ( 50) as a fifth-degree polynomial
in the variable cos 0.
the results of
Transcribed Image Text:ION 7.6 Double-angle and Half-angle Formulas 507 7.6 Assess Your Understanding 2V5 Concepts and Vocabulary 7. Multiple Choice Choose the expression that completes the Half-angle Formula for cosine functions: cos 1. cos (20) = cos 0 1-cos 0 cos a 1+ cos a 2. sin (a) t (b) + 2 (d) 1 cos 0 cos a sin a 1- cos a 3. tan5 (c) + (d) + V1 + cos a contain + and- 2 tan 0 4. True or False tan (20) = 1 tan e cos 0 then which 8. Multiple Choice If sin a = ±. s True or False sin (20) has two equivalent forms: 2 sin e cos 0 and sin? 0 - cos? A ( True or False tan (20) + tan (20) = tan(40) ormulas statement describes how e is related to a? (a) 0 = a (b) 0 = (c) 0 = 2a (d) 0 = a? Formula (9) Skill Building Problems 9-20, use the information given about the angle 0, 0se < 27, to find the exact value of: (a) sin (20) (b) cos (20) (c) sin (d) cos Double-angle Form 3 3 10. cos 0 = 5' 4 11. tan 0 = TT 0 < 0 < 5' >0 > 0 < 0 <T 3' T <0 < V3 37 3' 2 9. sin 0 = 2 37 12. tan 0 = 2' 1 T <0 < 13. cos e = - e < 27 14. sin 0 = 3' 2 in 16. csc e = - V5, cos e < 0 17. cot 0 = -2, sec 0 < 0 15. sec 0 = 3, sin 0 > 0 19. tan 0 = -3, sin e < 0 20. cot 0 = 3, cos 0 < 0 18. sec 0 = 2, csc 0 < 0 tan In Problems 21-30, use Half-angle Formulas to find the exact value of each expression. \21. sin 22.5° 22. cos 22.5° 23. tan 8 24. tan 8 157 27. sec 8 7 28. csc 8 26. sin 195° 25. cos 165° 37 30. cos 29. sin In Problems 31-42, f(x) = sin x, g(x) = cos x, and h(x) = tan x. Use the figures below to evaluate each function. y 31. f(20) 32. g(20) x2 + y2 = 5 x2 + y2 = 1 (х, 2) 3A. 33. gl 35. h(20) 36. nogab0 ne lo a o 38. f(2u) a T () 37. g(2a) 42. h(2a) 41. h 39. 40. A slumol tained as i 44. Show that sin (40) = (cos 0) (4 sin 0 – 8 sin° 0). 3 43. Show that sin“ 0 = 8 1 cos (20) + cos (46). 1 cos (80). 3 A 46. Show that sin" 0 cos“ e = 128 1 cos (40) + 128° 1 1 32 A 45. Show that sin? 0 cos² 0 cos (40). 48. Find an expression for cos ( 40) as a fourth-degree polynomial in the variable cos 0. 8 4%. Find an expression for cos ( 30) as a third-degree polynomial in the variable cos 0. 49. Find an expression for sin ( 50) as a fifth-degree polynomial in the variable sin 0. 50. Find an expression for cos ( 50) as a fifth-degree polynomial in the variable cos 0. the results of
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Swokowski
Publisher:
Cengage