0.1 Concepts Review 1. rational numbers - Calculus 9e Purcell Varberg Rigdon (Solution)

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CHAPTER

0 Preliminaries

0.1 Concepts Review

1. rational numbers 2. dense

3. If not Q then not P. 4. theorems

Problem Set 0.1

1. 4 2(8 11) 6 4 2( 3) 6 –4(37) –148

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16.

(

5 3

) ( ) ( )( ) ( )

2 5 2 2 5 3 3 2 single value satisfies 0

0=a. 31. _.083

12 1.000 96 40

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32. _.285714 7 2.000000

1 4

21 3.000000 2 1

17 5.000000... 0.2941176470588235 3 4

13 11.000000 10 4

1000 123.123123... 0.123123...

999 123

123 41 999 333 x 1000 217.171717...

10 2.171717...

990 215

215 43 990 198 x 100 256.565656...

2.565656... 100 392.929292...

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41. x = 0.199999... 100 19.99999...

10 1.99999...

90 18 100 39.99999...

10 3.99999...

90 36

43. Those rational numbers that can be expressed by a terminating decimal followed by zeros.

44. p p 1 ,

of any number of terminating decimals is also a terminating decimal, so (0.5) and (0.2) ,n m and hence their product, 1,

q is a terminating decimal. Thus p

q has a terminating decimal expansion.

45. Answers will vary. Possible answer: 0.000001,

12 1

0.0000010819...

π ≈

46. Smallest positive integer: 1; There is no smallest positive rational or irrational number. 47. Answers will vary. Possible answer:

3.14159101001...

48. There is no real number between 0.9999… (repeating 9's) and 1. 0.9999… and 1 represent the same real number.

49. Irrational

50. Answers will vary. Possible answers:

and , be a natural number that satisfies

a

b

n

<

−

/

1

. Let

S

=

{

k

:

k

n

>

b

}

. Since a nonempty set of integers that is bounded below contains a least element, there is a

S

58. Answers will vary. Possible answer: ≈120 in3

59. 4000 mi 5280 ft 21,120, 000 ft mi

r= × =

equator 2 2 (21,120, 000) 132, 700,874 ft

r

π π

= =

≈

60. Answers will vary. Possible answer:

beats min hr day

70 60 24 365 20 yr

min hr day year

735,840, 000 beats

× × × ×

93,807, 453.98 in. V = πr h= π⎛_⎜ ⋅ ⎞_⎟ ⋅

⎝ ⎠

≈

volume of one board foot (in inches):

3 1 12 12 144 in.× × =

number of board feet:

93,807, 453.98

651, 441 board ft

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62. V =π(8.004) (270)2 −π(8) (270)2 ≈54.3 ft.3

63. a. If I stay home from work today then it rains. If I do not stay home from work, then it does not rain.

b. If the candidate will be hired then she meets all the qualifications. If the candidate will not be hired then she does not meet all the qualifications.

64. a. If I pass the course, then I got an A on the final exam. If I did not pass the course, thn I did not get an A on the final exam. b. If I take off next week, then I finished my

research paper. If I do not take off next week, then I did not finish my research paper.

65. a. If a triangle is a right triangle, then

2 2 2

.

a +b =c If a triangle is not a right triangle, then a2+b2 ≠c2.

b. If the measure of angle ABC is greater than 0o and less than 90o, it is acute. If the measure of angle ABC is less than 0o_or greater than 90o, then it is not acute. 66. a. If angle ABC is an acute angle, then its

measure is 45o. If angle ABC is not an acute angle, then its measure is not 45o_. b. If a2 <b2 then a<b. If a2≥b2 then

. a≥b

67. a. The statement, converse, and contrapositive are all true. b. The statement, converse, and

contrapositive are all true.

68. a. The statement and contrapositive are true. The converse is false.

b. The statement, converse, and contrapositive are all false. 69. a. Some isosceles triangles are not

equilateral. The negation is true.

b. All real numbers are integers. The original statement is true.

c. Some natural number is larger than its square. The original statement is true. 70. a. Some natural number is not rational. The

original statement is true.

b. Every circle has area less than or equal to 9π. The original statement is true. c. Some real number is less than or equal to

its square. The negation is true.

71. a. True; If x is positive, then x2 is positive. b. False; Take x= −2. Then x2>0 but

0 x< .

c. False; Take 1 2

x= . Then

x

2

=

₄1

<

x

d. True; Let x be any number. Take

2 ₁

y=x + . Then y>x2.

e. True; Let y be any positive number. Take 2

y

x= . Then 0< <x y.

72. a. True; x+ − < + + −

( )

x x 1

( )

x : 0 1<

b. False; There are infinitely many prime numbers.

c. True; Let x be any number. Take

1 1 y

x

= + . Then y 1 x

> .

d. True; 1/n can be made arbitrarily close to 0.

e. True; 1/ 2n can be made arbitrarily close to 0.

73. a. If n is odd, then there is an integer k such that n=2k+1. Then

2 2 2

2

(2 1) 4 4 1

2(2 2 ) 1

n k k k

k k

= + = + +

= + +

b. Prove the contrapositive. Suppose n is even. Then there is an integer k such that

2 .

n= k Then n2 =(2 )k 2 =4k2=2(2k2). Thus n2 is even.

74. Parts (a) and (b) prove that n is odd if and only if n2 is odd.

75. a. 243= ⋅ ⋅ ⋅ ⋅3 3 3 3 3

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c.

2 2

5100 2 2550 2 2 1275 2 2 3 425 2 2 3 5 85 2 2 3 5 5 17 or 2 3 5 17

= ⋅ = ⋅ ⋅ = ⋅ ⋅ ⋅ = ⋅ ⋅ ⋅ ⋅ = ⋅ ⋅ ⋅ ⋅ ⋅ ⋅ ⋅ ⋅

76. For example, let A= ⋅b c2⋅d3; then

2 2 4 6

A =b ⋅c ⋅d , so the square of the number is the product of primes which occur an even number of times.

77.

2

2 2

2

2 p; 2 p ; 2q p ;

q _q

= = = Since the prime

factors of p2_{must occur an even number of}

times, 2q2_{would not be valid and}p ₂ q =

must be irrational.

78.

2

2 2

2

3 p; 3 p ; 3q p ;

q _q

= = = Since the prime

factors of p2must occur an even number of times, 3q2 would not be valid and p 3

q =

must be irrational.

79. Let a, b, p, and q be natural numbers, so a b

and p

q are rational.

a p aq bp

b q bq

+

+ = This

sum is the quotient of natural numbers, so it is also rational.

80. Assume a is irrational, p 0

q ≠ is rational, and

p r

a

q s

⋅ = is rational. Then a q r p s

⋅ =

⋅ is rational, which is a contradiction. 81. a. – 9=–3; rational

b. 0.375 3; 8

= rational

c. (3 2)(5 2)=15 4=30; rational d. (1+ 3)2= +1 2 3 3+ = +4 2 3;

irrational

82. a. –2 b. –2 c. x = 2.4444...;

10 24.4444... 2.4444...

9 22

22 9 x x x x

= = =

=

d. 1

e. n = 1: x = 0, n = 2: 3, 2

x= n = 3: – ,2 3

x=

n = 4: 5

4 x=

The upper bound is 3. 2

f. 2

83. a. Answers will vary. Possible answer: An example

isS ={ :x x2<5, a rational number}.x

Here the least upper bound is 5, which is real but irrational.

b. True

1. [ 1, 5); (− −∞ −, 2]

2. b > 0; b < 0 3. (b) and (c) 4. − ≤ ≤1 x 5

Problem Set 0.2

1. a.

b.

c.

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28. a. True. b. True. any positive number.

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51. 2 6 2 6 12

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63.

Conversely,

(

)

of absolute values.

c. a b c (a b) c a b c

by the Triangular Inequality, and since

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70. a. 2 square the area is

2

Problem 74,

2

so the square has the largest area.

76. 1 2 3 99 0;

0.01 0.01

100

4 4

0.01 0.01

100 100

4 4

0.00004 in

r

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Problem Set 0.3

1.

2 2

(3 – 1) (1 – 1) 4 2

d = + = =

2.

2 2

( 3 2) (5 2) 74 8.60

d = − − + + = ≈

3.

2 2

(4 – 5) (5 8) 170 13.04

d = + + = ≈

4.

2 2

( 1 6) (5 3) 49 4 53

d = − − + − = + =

≈

5. d₁= (5 2)+ 2+(3 – 4)2 = 49 1+ = 50

2 2

(5 10) (3 8) 25 25 50

2

2 2

( 2 10) (4 8) 3

144 16 160

so the triangle is isosceles.

1 2

d

d d

= − + − = + =

= − − + −

= + =

=

6. a= (2 4)− 2+ − −( 4 0)2 = 4 16+ = 20

2 2

(4 8) (0 2) 16 4 20

b= − + + = + =

2 2

(2 8) ( 4 2) 36 4 40

c= − + − + = + =

2 2 2_,

a +b =c so the triangle is a right triangle. 7. (–1, –1), (–1, 3); (7, –1), (7, 3); (1, 1), (5, 1) 8.

( )

2 2 2 2

2 2

( 3) (0 1) ( 6) (0 4) ;

6 10 12 52

6 42

7 7, 0

x x

x x x x

x x

− + − = − + −

− + = − +

= = ⇒

9. –2 4 –2 3, 1, 1 ;

2 2 2

+ +

⎛ ⎞ ⎛₌ ⎞

⎜ ⎟ ⎜ ⎟

⎝ ⎠ ⎝ ⎠

2

1 25

2

(1 2) – 3 9 3.91

2 4

d= + +⎛_⎜ ⎞_⎟ = + ≈

⎝ ⎠

10. midpoint of 1 2 3 6, 3 9,

2 2 2 2

AB=⎛_⎜ + + ⎞ ⎛_{⎟ ⎜}= ⎞_⎟

⎝ ⎠ ⎝ ⎠

4 3 7 4 7 11

midpoint of , ,

2 2 2 2

CD=⎛_⎜ + + ⎞ ⎛_{⎟ ⎜}= ⎞_⎟

⎝ ⎠ ⎝ ⎠

2 2

3 7 9 11

2 2 2 2

4 1 5 2.24

d = ⎛_⎜ − ⎞_⎟ +⎛_⎜ − ⎞_⎟

⎝ ⎠ ⎝ ⎠

= + = ≈

11 (x – 1)2 + (y – 1)2 = 1

12. 2 2 2

2 2

( 2) ( 3) 4

( 2) ( 3) 16

x y

+ + − =

13. 2 2 2

2 2 2

2

2 2

( 2) ( 1)

(5 2) (3 1)

9 16 25

( 2) ( 1) 25

x y r

r r

x y

− + + =

= + =

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(16)

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e. y− =2 3(x+3);

1 perpendicular slope ;

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47. 3 – 4 5

circumscribed circle:

2 2 the sum of half the circumference of the first circle, half the circumference of the second circle, and twice the distance between their centers.

2 2 midpoint of the hypotenuse is , .

2 2 a b

⎛ ⎞

⎜ ⎟

⎝ ⎠ The distances from the vertices are

2 2 2 2

which are all the same.

52. From Problem 51, the midpoint of the hypotenuse,

(

4,3, ,

)

is equidistant from the vertices. This is the center of the circle. The radius is 16 9+ =5. The equation of the circle is

2 2

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53. x2+y2– 4 – 2 – 11x y =0

center of first circle: (2, 1) center of second circle: (–10, 6)

2 2 the circles must not intersect if the distance between their centers is 13.

54. 2 2 similar because each contains a right angle and they share angle∠QRC. For an angle of

By the Pythagorean Theorem, we have

2 2 circles touch. This point must satisfy

2 2 2

At the same time, the point where the two circles touch must satisfy

2 2 2

Equating the two expressions for a yields

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57. Refer to figure 15 in the text. Given ine l1 with

slope m, draw ABC with vertical and horizontal sides m, 1.

Line l2 is obtained from l1 by rotating it

around the point A by 90° counter-clockwise. Triangle ABC is rotated into triangle AED. right triangle, with c the length of the

hypotenuse. Then the Pythagorean Theorem says that a2+b2=c2 diameter x, so the circles on the legs of the triangle have total area equal to the area of the semicircle on the hypotenuse.

From a2+b2=c2,

4 x is the area of an equilateral triangle

with sides of length x, so the equilateral triangles on the legs of the right triangle have total area equal to the area of the equilateral triangle on the hypotenuse of the right triangle.

60. See the figure below. The angle at T is a right angle, so the Pythagorean Theorem gives

2 2 2 corresponding distances between the centers of the circles:

2 2

Each circle has radius 2, so the part of the belt around the wheels is 38.8 units.

≈ + + + π

≈

62 As in Problems 50 and 61, the curved portions of the belt have total length 2πr. The lengths of the straight portions will be the same as the lengths of the sides. The belt will have length

1 2

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63. A = 3, B = 4, C = –6 figure below. The center of the circle is then

(

4−r r,

)

, so it has equation

2 2 2

(x− −(4 r)) +(y−r) =r . Along the side of length 5, the y-coordinate is always 3

4 times

the x-coordinate. Thus, we need to find the value of r for which there is exactly one x-solution to

2

Solving for x in this equation gives

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72. The line tangent to the circle at

( )

a b, will be

74. Use the formula given for problems 63-66, for

( ) ( )

x y, = 0, 0 .

76. See the figure below. The midpoints of the sides are

PS and QR are parallel. The slopes of SR and

PQ are both 3 1 parallelogram.

77. x2+( – 6)y 2 =25; passes through (3, 2) tangent line: 3x – 4y = 1

The dirt hits the wall at y = 8.

0.4 Concepts Review

1. y-axis 3. 8; –2, 1, 4 2.

(

4, 2−

)

4. line; parabola

Problem Set 0.4

1. y = –x2 + 1; y-intercept = 1; y = (1 + x)(1 – x); x-intercepts = –1, 1

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2. x= −y2+1; y-intercepts= −1,1; -intercept 1

x = .

Symmetric with respect to the x-axis.

3. x = –4y2_{– 1; x-intercept = –1}

Symmetric with respect to the x-axis

4. y=4x2−1; y-intercept= −1

1 1 (2 1)(2 1); -intercepts ,

2 2

y= x+ x− x = −

Symmetric with respect to the y-axis.

5. x2_{+ y = 0; y = –x}2

x-intercept = 0, y-intercept = 0 Symmetric with respect to the y-axis

6. y=x2−2 ; -interceptx y =0 (2 ); -intercepts 0, 2

y=x −x x =

7. 7x2_{+ 3y = 0; 3y = –7x}2_; _–7 2 3

y= x

x-intercept = 0, y-intercept = 0 Symmetric with respect to the y-axis

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9. x2_{+ y}2_{= 4}

x-intercepts = -2, 2; y-intercepts = -2, 2 Symmetric with respect to the x-axis, y-axis, and origin

10. 3x2+4y2 =12;y-intercepts = − 3, 3 -intercepts 2, 2

x = −

Symmetric with respect to the x-axis, y-axis, and origin

11. y = –x2 _{– 2x + 2: y-intercept = 2}

2 4 8 2 2 3

-intercepts –1 3

–2 –2

x = ± + = ± = ±

12. 4x2+3y2=12; y-intercepts= −2, 2

x-intercepts = − 3, 3

13. x2 – y2_{= 4}

x-intercept = -2, 2

14. x2+(y−1)2=9; -interceptsy = −2, 4

x-intercepts = −2 2, 2 2

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15. 4(x – 1)2_{+ y}2_{= 36;}

y-intercepts = ± 32= ±4 2

x-intercepts = –2, 4

16. x2−4x+3y2= −2

x-intercepts = 2± 2

17. x2_{+ 9(y + 2)}2_{= 36; y-intercepts = –4, 0}

x-intercept = 0

Symmetric with respect to the y-axis

18. x4+y4=1; -interceptsy = −1,1

x-intercepts 1,1= −

19. x4 + y4_{= 16; y-intercepts}_{= −}_{2, 2}

x-intercepts 2, 2= −

Symmetric with respect to the y-axis, x-axis and origin

20. y = x3 _{– x; y-intercepts = 0;}

y = x(x2_{– 1) = x(x + 1)(x – 1);}

x-intercepts = –1, 0, 1

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21.

2 1

; 1 y

x

=

+ y-intercept = 1

22. ₂ ; -intercept 0 1

x

y y

x

= =

+ x-intercept = 0

Symmetric with respect to the origin

23. 2– 2

2_– 2

2 2

2 4 3 12 –2

2( 2 1) 3( 4 4) –2 2 12

2( – 1) 3( 2) 12

x x y y

x y

+ + =

+ + + + = + +

+ + =

y-intercepts = –2 30 3

±

x-intercept = 1

24. 4

(

x−5

)

2+9(y+2)2=36; -interceptx =5

25. y = (x – 1)(x – 2)(x – 3); y-intercept = –6 x-intercepts = 1, 2, 3

26. y = x2_{(x – 1)(x – 2); y-intercept = 0}

x-intercepts = 0, 1, 2

27. y=x2(x−1) ;2 y-intercept = 0 x-intercepts = 0, 1

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28. y=x4(x−1) (4 x+1) ; -intercept4 y =0

x-intercepts 1, 0,1= −

29. x+ y =1; y-intercepts = –1, 1; x-intercepts = –1, 1

Symmetric with respect to the x-axis, y-axis and origin

30. x+ y =4; y-intercepts = –4, 4; x-intercepts = –4, 4

Symmetric with respect to the x-axis, y-axis and origin

31. 2

2 2

1 ( 1)

1 2 1

3 0

( 3) 0

0, 3

x x

x x x

x x

x x x

− + = +

− + = + +

+ =

+ = = −

Intersection points: (0, 1) and (–3, 4)

32. 2

2 2

2 3 ( 1)

2 3 2 1

4 0

x x

x x x

x

+ = − − + = − + − + =

No points of intersection

33. 2

2 2

2 3 2( 4)

2 3 2 16 32

2 18 35 0

x x

x x x

x − x

− + = − −

− + = − + −

+ =

18 324 – 280 18 2 11 9 11

;

4 4 2

x= ± = ± = ±

Intersection points: 9 – 11, – 6 11 , 2

⎛ ⎞

+

⎜ ⎟

⎝ ⎠

9 11

, – 6 – 11 2

⎛ + ⎞

⎜ ⎟

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34. 2

No points of intersection

35. 2 2

Intersection points:

3 3 6 2 3 6 3 3 6 2 3 6

1.65, 0.85 5

x=− ± ≈ −

2 39 1 3 39

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39. a. y=x2; (2)

Three such distances.

41. x2 + 2x + y2_{– 2y = 20;}

(

_{–2, 1}₊ _{21 ,}

)

1. domain; range

2. f(2 )u =3(2 )u 2=12u2; (f x+h)=3(x+h)2

3. asymptote

4. even; odd; y-axis; origin

Problem Set 0.5

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d.

(

) (

)

3

(

)

defined

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8. The graphs on the left are not graphs of functions, the graphs on the right are graphs of functions.

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17. F(x) = 2x + 1; F(–x) = –2x + 1; neither

18. F x( )=3 – 2; (– )x F x =–3 – 2;x neither

19. g x( )=3x2+2 – 1; (– )x g x =3x2– 2 – 1x ; neither

20.

3 3

( ) ; (– ) – ;

8 8

u u

g u = g u = odd function

21.

2 2

–

( ) ; (– ) ;

– 1 – 1

x x

g x g x

x x

= = odd

22. ( ) 2 1; (– ) –2 1;

– 1 – – 1

z z

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23. f w( )= w– 1; (– )f w = – – 1; w neither

24. h x( )= x2+4; (– )h x = x2+4; even function

25. f x( )= 2 ; (– )x f x = –2x = 2 ;x even function

26. F t( )=–t+3 ; (– )F t =– –t+3 ; neither

27. ( ) ; ( ) ;

2 2

x x

g x = g − = −x neither

28. G x( )= 2x−1 ; (G − = − +x) 2x 1 ; neither

29.

2

1 if 0

( ) 1 if 0 2

– 1 if 2 t

g t t t

t t

⎧ ≤

⎪

=⎨ + < < ⎪

≥ ⎩

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30.

2 exceeds its square by the maximum amount.

34. Each side has length .

base height

2 2 the height of the cylinder. From the figure,

r2+ h

39. The area of the two semicircular ends is

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40. a. (1) 1(1) 1(1)(2 1) 3

2 2

A = + − =

b. (2) 2(1) 1(2)(3 1) 4 2

A = + − =

c. A(0)=0

d. ( ) (1) 1( )( 1 1) 1 2

2 2

A c =c + c c+ − = c +c

e.

f. Domain:

{

c∈ :c≥0

}

Range:

{

y∈ :y≥0

}

41. a. B(0)=0

b. 1 1 (1) 1 1 1

2 2 2 6 12

B⎛ ⎞ =_{⎜ ⎟} B = ⋅ =

⎝ ⎠

c.

42. a. f(x + y) = 2(x + y) = 2x + 2y = f(x) + f(y) b. f x( +y)=(x+y)2=x2+2xy+y2

( ) ( )

f x f y

≠ +

c. f(x + y) = 2(x + y) + 1 = 2x + 2y + 1 ≠ f(x) + f(y)

d. f(x + y) = –3(x + y) = –3x – 3y = f(x) + f(y) 43. For any x, x + 0 = x, so

f(x) = f(x + 0) = f(x) + f(0), hence f(0) = 0. Let m be the value of f(1). For p in N,

1 1 1 ... 1, p= ⋅ = + + +p so

f(p) = f(1 + 1 + ... + 1) = f(1) + f(1) + ... + f(1) = pf(1) = pm.

1 1 1 1

1 p ... ,

p p p p

⎛ ⎞

= _{⎜ ⎟}= + + +

⎝ ⎠ so

1 1 1

(1) ...

m f f

p p p

⎛ ⎞

= = _⎜ + + + _⎟

⎝ ⎠

1 1 1 1

... ,

f f f pf

p p p p

⎛ ⎞ ⎛ ⎞ ⎛ ⎞ ⎛ ⎞

= _{⎜ ⎟}+ _{⎜ ⎟}+ + _{⎜ ⎟}= _{⎜ ⎟}

⎝ ⎠ ⎝ ⎠ ⎝ ⎠ ⎝ ⎠

hence f 1 m.

p p

⎛ ⎞ = ⎜ ⎟

⎝ ⎠ Any rational number can be written as p

q with p, q in N.

1 1 1 1

... , p

p

q q q q q

⎛ ⎞

= _{⎜ ⎟}= + + +

⎝ ⎠

so f p f 1 1 ... 1

q q q q

⎛ ⎞ ⎛ ⎞

= + + +

⎜ ⎟ ⎜ ⎟

⎝ ⎠ ⎝ ⎠

1 1 1

...

f f f

q q q

⎛ ⎞ ⎛ ⎞ ⎛ ⎞

= _{⎜ ⎟}+ _{⎜ ⎟}+ + _{⎜ ⎟}

⎝ ⎠ ⎝ ⎠ ⎝ ⎠

1 m p

pf p m

q q q

⎛ ⎞ ⎛ ⎞ ⎛ ⎞

(36)

44. The player has run 10t feet after t seconds. He reaches first base when t = 9, second base when t = 18, third base when t = 27, and home plate when t = 36. The player is 10t – 90 feet from first base when 9≤t≤18, hence

2 2

90 +(10t−90) feet from home plate. The player is 10t – 180 feet from second base when

18≤t≤27, thus he is

90 – (10t – 180) = 270 – 10t feet from third base and 902+(270 10 )− t 2 feet from home plate. The player is 10t – 270 feet from third base when 27≤ ≤t 36, thus he is

90 – (10t – 270) = 360 – 10t feet from home plate.

a.

2 2

10 if 0 9

90 (10 90) if 9 18

90 (270 10 ) if 18 27

360 – 10 if 27 36

t t

s

t t

≤ ≤ ⎧

⎪

⎪ + − < ≤

⎪ = ⎨

⎪ ₊ ₋ _{< ≤}

⎪

< ≤ ⎪⎩

b. 2 2

2 2

180 180 10 if 0 9

or 27 36

90 (10 90) if 9 18

90 (270 10 ) if 18 27

t t

t

s t t

t t

⎧ − − ≤ ≤

⎪ _{< ≤}

⎪ ⎪⎪

=⎨ + − < ≤

⎪

+ − < ≤

⎪ ⎪ ⎪⎩

45. a. f(1.38) ≈ 0.2994 f(4.12) ≈ 3.6852

b. x f(x)

–4 –4.05

–3 –3.1538

–2 –2.375

–1 –1.8

0 –1.25

1 –0.2

2 1.125

3 2.3846

4 3.55

46. a. f(1.38) ≈ –76.8204 f(4.12) ≈ 6.7508

b. x f(x)

–4 –6.1902

–3 0.4118

–2 13.7651

–1 9.9579

0 0

1 –7.3369

2 –17.7388

3 –0.4521

4 4.4378

47.

a. Range: {y ∈ R: –22 ≤ y ≤ 13} b. f(x) = 0 when x ≈ –1.1, 1.7, 4.3

(37)

b. f(x) ≥ g(x) on [-0.6, 3.0] ∪ [4.6, 5]

c. f x( ) – ( )g x

3_{– 5} 2 _{8 – 2} 2 ₈ ₁

x x x x x

= + + + +

3_{– 7} 2 ₉ ₉

x x x

= + +

Largest value f(–2) – (–2)g =45

49.

a. x-intercept: 3x – 4 = 0; x=4

3

y-intercept: 2

3 0 – 4 2 3 0 0 – 6

⋅ = +

b.

c. x2+x– 6=0; (x + 3)(x – 2) = 0 Vertical asymptotes at x = –3, x = 2

d. Horizontal asymptote at y = 0

50.

a. x-intercepts:

2 4 2 3

3 – 4 0;

3 3

x = x= ± = ±

y-intercept: 2

3

b. On ⎡⎣− −6, 3

)

, g increases from

( )

13

6 4.3333

3

g − = ≈ to ∞. On

(

2, 6⎤⎦, g

decreased from ∞ to 26 2.8889

9 ≈ . On

(

−3, 2

)

the maximum occurs around

0.1451

x= with value 0.6748 . Thus, the

range is

(

−∞, 0.6748⎤ ⎡_{⎦ ⎣}∪ 2.8889,∞

)

.

c. x2+x– 6=0; (x + 3)(x – 2) = 0 Vertical asymptotes at x = –3, x = 2

d. Horizontal asymptote at y = 3

1. (x2+1)3

2. f(g(x))

3. 2; left

4. a quotient of two polynomial functions

Problem Set 0.6

1. a. (f +g)(2)=(2 3) 2+ + 2 =9

b. (f g⋅ )(0)=(0 3)(0 )+ 2 =0

c.

2

3 9 3

( )(3)

3 3 6 2

g f = = =

+

d. (f g)(1)= f(12)=1+3=4

e. (g f)(1)=g(1+3)=42 =16

f. (g f)(–8)=g(–8+3)=(–5)2 =25

2. a. ( – )(2) (22 2) – 2 6 –2 28

2 3 5 5

f g = + = =

+

b. ( )(1) 1 1 2 4 4 2 3 1

2 2

= = + =

+

g f

c. ₉

1 3 1 3 3

2 ) 3 (

2 2

2 _⎟ ₌

⎠ ⎞ ⎜ ⎝ ⎛ = ⎥⎦ ⎤ ⎢⎣ ⎡

+ =

(38)

(39)

15. Translate the graph of g(x)= x to the right 2 units and down 3 units.

16. Translate the graph of h x( )= x to the left 3 units and down 4 units.

17. Translate the graph of y=x2 to the right 2 units and down 4 units.

18. Translate the graph of y=x3 to the left 1 unit and down 3 units.

19. ( )( ) – 3 2

x

f +g x = + x

(40)

21. F t( ) t –t functions.

b. Odd;

(f + g)(–x) = f(–x) + g(–x) = –f(x) – g(x) = –(f + g)(x) if f and g are both odd functions.

c. Even; function.

24. a. F(x) – F(–x) is odd because

25. Not every polynomial of even degree is an

even function. For example f(x)=x2+x is neither even nor odd. Not every polynomial of odd degree is an odd function. For example

(41)

(42)

(43)

40.

41. a.

b.

c.

42.

1. (–∞, ∞); [–1, 1]

Problem Set 0.7

1. a. 30

c. –66.6 –1.1624

180

π ⎛ _{⎞ ≈}

⎜ ⎟

⎝ ⎠

d. 240.11 4.1907 180

π ⎛ _{⎞ ≈}

⎜ ⎟

⎝ ⎠

e. –369 –6.4403

(44)

4. a. 3.141 180

then the triangle in the figure below is

equilateral. Thus, 1 1

2 2

PQ = OP = . This

implies that sin 1

6 2

π ₌

. By the Pythagorean

Identity,

2 sin cos

4 4 2

π ₌ π ₌

were derived in the text.

If the angle is / 3π then the triangle in the

figure below is equilateral. Thus cos 1

3 2

π =

and by the Pythagorean Identity, sin 3

3 2

obtained using the same kind of reasoning in the second quadrant.

(45)

e.

( )

cos cos

t

cos cos

t t

sec sec

t

csc sec

u u

csc csc

(46)

b. y=2sint

c. cos

4

y= ⎛_⎜x−π⎞_⎟

⎝ ⎠

d. y=sect

15. a. y = csc t

b. y = 2 cos t

c. y=cos 3t

d. cos

3

y= ⎛_⎜t+π⎞_⎟

⎝ ⎠

16. y=3 cosx 2

(47)

17. y = 2 sin 2x

Period = π, amplitude = 2

18. y = tan x

Period = π

19. cot(2 ) 6 1

2 x

y= +

Period =

2

π

, shift: 2 units up

20. y= +3 sec(x−π)

Period = 2π, shift: 3 units up, πunits right

21. y=21+7sin(2x+3)

Period = π , amplitude = 7, shift: 21 units up,

2 3

units left

22. 3cos – – 1 2

y= ⎛_⎜x π⎞_⎟

⎝ ⎠

Period = 2π, amplitude = 3, shifts: π

2 units

right and 1 unit down.

23. y=tan 2x–π 3

⎛ ⎝

⎜ ⎞

⎠ ⎟

Period = π

2, shift:

π

(48)

24. a. and g.: sin cos – cos( – )

cos cos

3 3 2 4

sin sin

6 6 2 4

sin sin

6 6 2 8

60 5280

(49)

39. a. tanα= 3 tan tan

1 tan tan 1

tan –7; 1.7127

1 (–2)

θ = = θ ≈

+

42. Recall that the area of the circle is πr2. The

measure of the vertex angle of the circle is2π.

Observe that the ratios of the vertex angles must equal the ratios of the areas. Thus,

2,

44. Divide the polygon into n isosceles triangles by

drawing lines from the center of the circle to the corners of the polygon. If the base of each triangle is on the perimeter of the polygon, then

the angle opposite each base has measure 2 .

n π

Bisect this angle to divide the triangle into two right triangles (See figure).

sin so 2 sin and cos

cos sin 2

45. The base of the triangle is the side opposite the

angle t. Then the base has length 2 sin

2

t r

(similar to Problem 44). The radius of the

semicircle is sin

(50)

46. cos cos cos cos

cos cos cos cos

4 4x 4x 16x 16x

⎡ ⎤ ⎡ ⎤

= _⎢ + _{⎥ ⎢} + _⎥

⎣ ⎦ ⎣ ⎦

1 3 3 3 1

cos cos cos cos

4 4x 16x 4x 16x

cos cos cos cos

4 2 16 16x 2 16x 16x

cos cos cos cos

2 16x 16x 2 16x 16x

cos cos cos cos

16x 16x 16x 16x

⎤

+ + + +

⎥⎦

47. The temperature function is

⎟⎟

The normal high temperature for November 15th is then T(10.5)=67.5°F. wheel will move around the circle of radius 2.

a. x(2)≈1.902

50. Both functions have frequency

10 2π

. When

you add functions that have the same frequency, the sum has the same frequency.

(51)

51. a. Csin(ω φt+ )=( cos )sinC φ ωt+( sin ) cosC φ ωt.Thus A= ⋅C cosφand B= ⋅C sinφ.

cos cos cos

sin sin sin

A A A A

d. Written response. Answers will vary.

52. ( a.), (b.), and (c.) all look similar to this:

the function oscillates too much over the domain plotted. Plots in (d) or (e) show the

53. a.

b.

c.

The plot in (a) shows the long term behavior of

the function, but not the short term behavior,

whereas the plot in (c) shows the short term

(52)

54. a.

(

)

2 2

( ) ( )

3

cos(100 ) 2 100

1

cos (100 ) 1 100

h x f g x

x

=

+ =

⎛ ⎞ ₊

⎜ ⎟

⎝ ⎠

2

1 3 2

( ) ( )( ) cos 100

100 ₁

x j x g f x

x +

⎛ ⎞

= = _⎜ _⎟

+

⎝ ⎠

b.

c.

55.

( )

(

)

(

)

1 4 1 : ,

4

4 7 1

: , 1

3 3 4

x x x n n

f x

x x x n n

⎧ _⎡ _⎞

− + ∈ +

⎪ ⎢ ⎟

⎪ ⎣ ⎠

= ⎨

⎡ ⎞

⎪− − + ∈_⎢ + _{+ ⎟}

⎪ _⎣ _⎠

⎩

where n is an integer.

2

1 x

y

−1 1

56.

( ) (

2

)

2, 2 1, 2 1

4 4

0.0625, otherwise

f x =⎧_⎪ x− n x∈_⎢⎡ n− n+ ⎤_⎥

⎨ ⎣ ⎦

⎪ ⎩

where n is an integer.

−2 0.5

1 x

y

−1 2

0.25

0.8 Chapter Review

Concepts Test

1. False: p and q must be integers.

2. True: 1 2 1 2 2 1

1 2 1 2

;

p p p q p q

q q q q

−

− = since

1, ,1 2, and 2

p q p q are integers, so are p q1 2−p q2 1 and q q1 2.

3. False: If the numbers are opposites

(–π and π) then the sum is 0, which is rational.

4. True: Between any two distinct real

numbers there are both a rational and an irrational number.

5. False: 0.999... is equal to 1.

6. True:

( ) ( )

am n = an m=amn

7. False: ( * ) *a b c=abc; *( * )a b c =abc

8. True: Since x≤ ≤y z and x≥z x, = =y z

9. True: If x was not 0, then

2

x

ε = would

(53)

10. True: y− = − −x (x y)so common.

13. True: If (a, b) and (c, d) share a point then

opposite signs then either

– – (– ) inequality is easily seen to be true.

22. True: If y is positive, thenx= ysatisfies

( )

2

2 _.

x = y =y

23. True: For every real number y, whether it

is positive, zero, or negative, the cube root _x₌3_y_satisfies

(54)

27. True; 3( )

they have equal slope. Then the reciprocals of the slopes are also equal.

29. True: If ab > 0, a and b have the same sign, so (a, b) is in either the first or third quadrant.

30. True: Let x=ε/ 2. If ε>0, then x>0

are on the same horizontal line.

33. True: 2 2

cannot be written in point-slope form.

35. True: This is the general linear equation.

36. True: Two non-vertical lines are parallel

if and only if they have the same slope.

37. False: The slopes of perpendicular lines

are negative reciprocals.

38. True: If a and b are rational and which is the equation of a straight line unless 3 2 and 6+ m m−2 are both 0, and there is no real number

(55)

53. True:

62. False: The domain of the tangent function

excludes all nπ +π

2 where n is an integer.

63. False: The cosine function is periodic, so

cos s = cos t does not necessarily imply s = t; e.g.,

cos 0=cos 2π =1, but 0≠2 .π

Sample Test Problems

(56)

4. x=4.1282828…

1000 4128.282828

10 41.282828

5. Answers will vary. Possible answer:

(57)

21. |t – 5| = |–(5 – t)| = |5 – t|

triangle.

(58)

b. 2; 3

2

1 ( 1)

3

2 5

3 3

m

y x

=

+ = −

= −

c. y=9

d. x = –3

31. a. 3 – 1 2; 7 2 9

m= =

+

2

–1 ( 2)

9

2 13

9 9

y x

= +

b. 3 – 2 5

–2 –3 5

3 5

– ;

2 2

x y

y x

=

= +

=

3 2

m=

3

–1 ( 2)

2 3

4 2

y x

= +

c. 3x + 4y = 9 4y = –3x + 9;

3 9

– ;

4 4

y= x+ 4

3

m=

4

–1 ( 2)

3

4 11

3 3

y x

= +

d. x = –2

e. contains (–2, 1) and (0, 3); 3 –1;

0 2

m= + y = x + 3

32. ₁ ₂

3

3 1 4 11 3 8 4

; ;

5 2 3 11 5 6 3

11 1 12 4

11 2 9 3

m m

m

+ −

= = = = =

− −

+

= = =

− 1 2 3,

m =m =m so the points lie on the same

line.

33. The figure is a cubic with respect to y. The equation is (b) x=y3.

34. The figure is a quadratic, opening downward,

with a negative y-intercept. The equation is (c)

2 _.

y=ax +bx+c with a < 0, b > 0, and c < 0.

(59)

36. 2 2

points of intersection: (0, 4) and (3, 7)

(60)

44. a.

2 2

3(– ) 3

(– ) – ;

(– ) 1 1

x x

f x

x x

= =

+ + odd

b. g(– )x = sin(– )x +cos(– )x

sinx cosx sinx cos ;x

= − + = + even

c. h(– )x =(– )x3+sin(– )x =–x3– sinx; odd

d.

2 2

4 4

(– ) 1 1

(– ) ;

– (– )

x x

k x

x x x x

+ +

= =

+ + even

45. a. f(x)=x2– 1

b. g(x)= x

x2+1

c. h(x)= x

2 _{if 0}_≤ _x_≤₂

6 –x if x>2

⎧ ⎨ ⎩

46.

47. V(x) = x(32 – 2x)(24 – 2x) Domain [0, 12]

48. a. ( )(2) 2 –1 (22 1) 13

2 2

f +g =⎛_⎜ ⎞_⎟+ + =

⎝ ⎠

b. ( )(2) 3 (5) 15

2 2

f g⋅ =⎛ ⎞_{⎜ ⎟} = ⎝ ⎠

c.

5 24 5 1 – 5 ) 5 ( ) 2 )(

(f g = f = =

d.

4 13 1 2 3 2 3 ) 2 )( (

2 = + ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ = ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ =g f

g

e.

3 3_(–1) _–1 1 ₀

1

f =⎛_⎜ + ⎞_⎟ =

⎝ ⎠

f.

2 2₍₂₎ 2₍₂₎ 3 ₍₅₎2

2

9 109

25

4 4

f +g =⎛ ⎞_{⎜ ⎟} + ⎝ ⎠

= + =

49. a. y= 1

4x

(61)

b. y= 1

4(x+2)

2

c. –1 1( 2)2 4

y= + x+

50. a. (−∞,16]

b. f g= 16–x4; domain [–2, 2]

c. g f =( 16–x)4 =(16–x)2;

domain (−∞,16]

(note: the simplification

4 2

( 16 – )x =(16 – )x is only true given

the restricted domain)

51. f x( )= x g x, ( ) 1= +x h x, ( )=x2,k(x) = sin x,

k h g f x x

F( )= 1+sin2 =

52. a. sin(570 ) sin(210 ) –1 2

° = ° =

b. cos 9 cos 0

2 2

π π

⎛ ⎞₌ ⎛ ⎞₌

⎜ ⎟ ⎜ ⎟

⎝ ⎠ ⎝ ⎠

c. cos –13 cos 3

6 6 2

π π

⎛ ⎞₌ ⎛₋ ⎞₌

⎜ ⎟ ⎜ ⎟

⎝ ⎠ ⎝ ⎠

53. a. sin (–t) = –sin t = –0.8

b. sin2t+cos2t=1

2 2

cos t=1 – (0.8) =0.36

cost=–0. 6

c. sin 2t = 2 sin t cos t = 2(0.8)(–0.6) = –0.96

d. tan sin 0.8 –4 –1.333

cos –0.6 3

t t

t

= = = ≈

e. cos – sin 0.8

2 t t

π

⎛ _{⎞ =} ₌

⎜ ⎟

⎝ ⎠

f. sin(π + = −t) sint= −0.8

54. sin 3t=sin(2t+ =t) sin 2 cost t+cos 2 sint t

2 2

2sin cost t (1 – 2sin t) sint

= +

2 3

2sin (1 – sint t) sin – 2sint t

= +

3 3

2sin – 2sint t sin – 2sint t

= +

3

3sin – 4sint t

=

55. s=rt

rev rad 1 min

9 20 2 (1 sec) 6

min rev 60 sec

⎛ ⎞⎛ ⎞⎛ ⎞

= _⎜ _⎟⎜ π _⎟⎜ _⎟ = π

⎝ ⎠⎝ ⎠⎝ ⎠

≈ 18.85 in.

Review and Preview Problems

1. a) 0<2x<4; 0< <x 2

b) − < <6 x 16

2. a) 13 2< x<14; 6.5< <x 7

b) − < −4 x/ 2<7; −14< <x 8

3. 7 3 or 7 3

10 or 4

x x

− = − = −

= =

4. 3 2 or 3 2

1 or 5

x x

+ = + = −

= − = −

5. 7 3 or 7 3

10 or 4

x x

− = − = −

= =

6. 7 or 7

7 or 7

x d x d

− = − = −

= + = −

7. a) 7 3 and 7 3

10 and 4

x x

− < − > −

(62)

b) 7 3 and 7 3

2.01 and 1.99

1.99 2.01

x x

0.9801 1

0.99 1.99

0.99 1 0.998001 1

0.999 1.999

.999 1 1.002001 1

1.001 2.001

1.001 1 1.0201 1

1.01 2.01

1.01 1

0.9 0.0357143

0.99 0.0033557

0.999 0.000333556

1.001 0.000333111

1.01 0.00331126

1.1 0.03125

1

0.1 0.998334

0.01 0.999983

0.001 0.99999983

0.01 0.999983

0.1 0.998334

1 0.841471

(63)

CHAPTER

1 Limits

1. L; c

Problem Set 1.1

1.

lim lim

– 2 – 2

lim lim

(64)

15.

4 2 2 2

2 2

3 3

–18 81 ( – 9)

lim lim

( – 3) ( – 3)

lim lim

( –1) ( –1)

lim lim

4

lim lim

2

0.1 0.499167

0.01 0.499992

0.001 0.49999992

–1. 0.420735

–0.1 0.499167

–0.01 0.499992

–0.001 0.49999992

0

0.1 0.0249792

0.01 0.00249998

0.001 0.00024999998

–1. –0.229849

–0.1 –0.0249792

–0.01 –0.00249998

–0.001 –0.00024999998

0

1. 0.0251314

0.1 2.775 10× −6

0.01 _0.0000249996

0.001 2.5 10× −7

–1. _0.211322

–0.1 _0.00249584

–0.01 _0.0000249996

(65)

24. x x−sin(_x₋x₃− −3) 3

4. 0.158529

3.1 _0.00166583

3.01 _0.0000166666

3.001 1.66667 10× −7

2. _0.158529

2.9 _0.00166583

2.99 _0.0000166666

2.999 1.66667 10× −7

lim 0.25

(66)

(67)

36. f x( ) x

lim lim

(68)

52. 0

sin 5 5 lim

3 3

x

x x

→ =

53. 0

1 lim cos

x→ x

⎛ ⎞ ⎜ ⎟

⎝ ⎠ does not exist.

54. 0

1

lim cos 0

x→ x ⎛ ⎞ =⎜ ⎟_{⎝ ⎠}x

55.

3

1

lim 6

2 2 2

x

→

− ₌

+ −

56. ₂

0

sin 2

lim 2

sin( )

x

x x

x

→ =

57.

–

2

– – 2

lim –3

– 2 x

x x

x

→ =

58. _1/( ₁₎ 1

2

lim 0

1 2 x

x→+ −

= +

59. 0

lim ; x

x

→ The computer gives a value of 0, but

0

lim x

x −

→ does not exist.

1. L–ε; L+ε

2. 0< x–a <δ; f(x) –L <ε

3. ε

3

4. ma + b

Problem Set 1.2

1. 0< t–a <δ ⇒ f(t)–M <ε

2. 0< u–b < ⇒δ g u( ) –L <ε

3. 0< z–d <δ ⇒ h(z)–P <ε 4. 0< y–e<δ ⇒φ(y)–B<ε

5. 0<c–x<δ ⇒ f(x)–L <ε

6. 0<t–a<δ ⇒ g(t)–D<ε

7. If x is within 0.001 of 2, then 2x is within 0.002 of 4.

8. If x is within 0.0005 of 2, then x2is within 0.002 of 4.

9. If x is within 0.0019 of 2, then

8 x

is within

0.002 of 4.

10. If x is within 0.001 of 2, then

x

8

is within 0.002

of 4.

11. 0< x– 0 < ⇒δ (2 – 1) – (–1)x <ε

2 – 1 1x + < ⇔ε 2x <ε

2 x ε

⇔ <

2

x ε

⇔ <

; 0 – 0

2 x

ε

δ = < <δ

(69)

(70)

5

0.65 1.65

(71)

(72)

29. Choose ε > 0. Since lim Combine the inequalities and use the fact thatf x( )≤g x( ) to get

L – ε < f(x) ≤ g(x) < M + ε which leads to L – ε < M + ε or L – M < 2ε.

However, L – M = α > 2ε

which is a contradiction. ThusL≤M.

31. (b) and (c) are equivalent to the definition of limit.

on the interval [2.75, 3.25], we see that

3 2

1. 48 2. 4

3. – 8; – 4 + 5c 4. 0

Problem Set 1.3

(73)

(74)

12. lim

lim lim

( 1)( 2)( 7) 7

lim lim

2 2

lim lim

(75)

27. lim3 ( )[ ( )+3]= lim3 ( )⋅lim[ ( )+3]

lim lim

(76)

Thus, lim

Using statement 6 and the above result,

( ) 1

lim lim lim lim

x c x c x c x c

lim lim

– 9

lim lim

( – 3)( 3) 3

No value satisfies this equation, so lim x→a

f(x) must not exist.

50. R has the vertices ±x

lim lim

(77)

51. a. NO= (0 – 0)2+(1 – 0)2 =1

perimeter of lim

perimeter of x

lim lim lim

area of

1. 0 2. 1

3. the denominator is 0 when t=0. 4. 1

Problem Set 1.4

1.

lim lim lim

sin sin cos

0

lim lim lim

2 2 3 2 3

cos sin cos lim

lim cos cos

2 θ sin

lim lim

(78)

13.

0 0

sin(3 ) 4 sin 3 4

lim lim

sec sec sec

sin 3 4

lim lim

sec sec

sin 3

sin sin sin

lim lim

2

0 0

sin sin

lim lim 1 1 1

the proof of the theorem. Then

0 0

0 0 0

lim cos lim cos( )

lim (cos cos sin sin ) lim cos lim cos sin lim sin cos

lim lim lim

(79)

24. a. Written response

lim 0.75

t

1. x increases without bound; f(x) gets close to L as x increases without bound

2. f(x) increases without bound as x approaches c from the right; f(x) decreases without bound as x approaches c from the left

3. y = 6; horizontal 4. x = 6; vertical

Problem Set 1.5

1.

lim lim

( – 5)(3 – ) ₈ ₁₅

lim lim

1 –

lim lim

3_{– 5} 2 _–5

lim lim

2

lim lim

2 7 2 7

lim lim

4 4

lim lim

(80)

16.

lim lim

1 1

lim lim

2 3 2 5

lim lim

2 2

lim lim

1

lim lim

(81)

33. As x→3 , 27,− x3→ while x−3→0−.

lim lim

– 3 – 3

lim lim

( 2)( – 2) Horizontal asymptote y = 0.

–

Vertical asymptote x = –1

44.

Horizontal asymptote y = 0.

2 – 2

Vertical asymptote x = –1

45.

Horizontal asymptote y = 2

–

(82)

46.

2 _– 2

Since 2x2+7>0 for all x, g(x) has no vertical asymptotes.

48. asymptotes.

49. f(x)=2x+3 – 1

positive number M there corresponds an N > 0 such that N < x ⇒ f(x) > M. b. We say that lim

x→–∞

f(x)= ∞ if to each positive number M there corresponds an N < 0 such that x < N ⇒ f(x) > M. 53. Let ε > 0 be given. Since lim

x→∞

f(x)=A, there is a corresponding number M₁ such that

1 ( ) – .

(83)

55. a. lim

x→∞

sinx does not exist as sin x oscillates between –1 and 1 as x increases.

(84)

1. lim ( )

x c

f x

→

2. every integer 3.

Problem Set 1.6

1. continuous at 3.

4.

continuous at 3.

5.

continuous at 3.

6. h(3) does not exist, so h(t) is not continuous at 3.

lim lim

– 3 – 3

continuous 12. From Problem 11,

continuous at 3 because

3

lim lim

3 – 3 –

lim lim

– 1 ( – 1)( 1)

lim lim

2

lim lim

(85)

23.

2

–1 –1

– 1 ( – 1)( 1)

lim sin lim sin

1 1

x x

x x x

x x

→ →

⎛ ⎞ _⎛ ₊ _⎞

=

⎜ ⎟ _⎜ _⎟

⎜ ₊ ⎟ _⎝ ₊ _⎠

⎝ ⎠

–1

lim sin( – 1) sin(–1 – 1) sin( 2) – sin 2 x

x →

= = = − =

Define F(–1) = –sin 2. 24. Discontinuous at x=π,30

25.

2 33 – ( )

( – )( – 3) x f x

x x

= π

Discontinuous at x=3,π 26. Continuous at all points 27. Discontinuous at all θ =nπ + π

2 where n is any

integer.

28. Discontinuous at all u≤ −5

29. Discontinuous at u = –1 30. Continuous at all points

31. ( ) 1

(2 – )(2 ) G x

x x

=

+

Discontinuous on (−∞ − ∪, 2] [2, )∞

32. Continuous at all points since

0

lim ( ) 0 (0)

x

f x f

→ = = and xlim1 ( ) 1 (1).

f x f

→ = =

33.

0

lim ( ) 0 (0) x

g x g

→ = =

–

1 1

lim ( ) 1, lim ( ) –1

x x

g x g x

+

→ →

= =

lim

x→1g(x) does not exist, so g(x) is discontinuous

at x = 1.

34. Discontinuous at every integer 35. Discontinuous at t = 1

2

n+ where n is any integer 36.

37.

38.

39.

40.

Discontinuous at all points except x = 0, because

lim ( ) ( ) x c

f x f c

→ ≠ forc≠0. xlimc ( ) f x

→ exists only

at c = 0 and

0

lim ( ) 0 (0)

x

f x f

→ = = .

41. Continuous.

42. Discontinuous: removable, define f(10)=20

43. Discontinuous: removable, define f(0)=1

44. Discontinuous: nonremovable.

45. Discontinuous, removable, redefine g(0)=1

(86)

47. Discontinuous: nonremovable.

48. Discontinuous: removable, define f(4)=4

49. The function is continuous on the intervals

(

0,1 , (1, 2], (2,3],

]

…

Length of call in minutes Cost $

0.24 0.36 0.12 0.48 0.60 0.72

1 2 3 4 5 6

[0, 200], (200, 300], (300, 400],…

Cost $

20 40 60 80

100 200 300 400 500 Miles Driven

(0, 0.25], (0.25, 0.375], (0.375, 0.5],…

Cost $

1 2 3 4

0.25 0.5 0.75 1 Miles Driven

52. Let f x( )=x3+3x−2. f is continuous on [0, 1]. f(0) = –2 < 0 and f(1) = 2 > 0. Thus, there is at least one number c between 0 and 1 such that

x3+3x−2=0.

53. Because the function is continuous on

[

0,2π

]

and

3 5

(cos 0)0 +6 sin 0 – 3=–3<0,

3 5 3

(cos 2 )(2 )π π +6 sin (2 ) – 3π = π8 – 3>0, there is at least one number c between 0 and 2π such that (cos )t t3+6 sin5t– 3=0.

54. Let

( )

=

3

−

7

2

+

14 −

8 x

x

f

. f(x) is

continuous at all values of x. f(0) = –8, f(5) = 12

Because 0 is between –8 and 12, there is at least one number c between 0 and 5 such that

( )

=

3

−

7

2

+

14 −

8 =

0 x

x

f

.

This equation has three solutions (x = 1,2,4)

55. Let f x

( )

= x−cos .x. f(x) is continuous at all values of x ≥ 0. f(0) = –1, f(π/2) = π/ 2

Because 0 is between –1 and π/ 2, there is at least one number c between 0 and π/2 such that

( )

cos 0.

f x = x− x=

The interval [0.6,0.7] contains the solution.

56. Let f x( )=x5+4x3– 7x+14

f(x) is continuous at all values of x. f(–2) = –36, f(0) = 14

Because 0 is between –36 and 14, there is at least one number c between –2 and 0 such that

5 3

( ) 4 – 7 14 0.

(87)

57. Suppose that f is continuous at c, so

Suppose that lim t→0

60. For f(x) to be continuous everywhere, f(1) = a(1) + b = 2 and f(2) = 6 = a(2) + b f(x) is continuous since the string is unbroken. Since 0≤a b, ≤1, f(x) satisfies the conditions of Problem 59, so there is some c in [0, 1] with f(c) = c, i.e., the point of string originally at c ends up at c.

62. The Intermediate Value Theorem does not imply the existence of a number c between –2 and 2 such that f c( )=0. The reason is that the function f x( ) is not continuous on

[

−2, 2 .

]

63. Let f(x) be the difference in times on the hiker’s watch where x is a point on the path, and suppose

0 continuous, f(x) is continuous, hence there is some c between 0 and 1 where f(c) = 0. This c is the point where the hiker’s watch showed the same time on both days.

64. Let f be the function on ⎢⎣⎡0,₂⎥⎦⎤ π

such that f(θ) is the length of the side of the rectangle which makes angle θ with the x-axis minus the length of the sides perpendicular to it. f is continuous on

⎥⎦ Intermediate Value Theorem, there is an angle

θ₀ between 0 and

2 π

such that f(θ₀)=0.

Hence, D can be circumscribed by a square. 65. Yes, g is continuous at R.