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1 When you see… Find the zeros You think…

1 When you see… Find the zeros You think…. 2 To find the zeros

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Page 1: 1 When you see… Find the zeros You think…. 2 To find the zeros

1

When you see…

Find the zeros

You think…

Page 2: 1 When you see… Find the zeros You think…. 2 To find the zeros

2

To find the zeros...To find the zeros...

Set function = 0 Factor or use quadratic equation if quadratic. Graph to find zeros on calculator.

Page 3: 1 When you see… Find the zeros You think…. 2 To find the zeros

3

When you see…

Find equation of the line tangent to f(x) at (a, b)

You think…

Page 4: 1 When you see… Find the zeros You think…. 2 To find the zeros

4

Equation of the tangent lineEquation of the tangent line

Point and Slope (a, f(a)) f ’(a)

Use y- y1 = f ’(a)( x – x1 )

Page 5: 1 When you see… Find the zeros You think…. 2 To find the zeros

5

You think…

When you see…

Find equation of the line normal to f(x) at (a, b)

Page 6: 1 When you see… Find the zeros You think…. 2 To find the zeros

6

Equation of the normal lineEquation of the normal line

Point and Slope (a, f(a)) m = - 1 f ’(a) Use y- y1 = m( x – x1 )

Page 7: 1 When you see… Find the zeros You think…. 2 To find the zeros

7

You think…

When you see…

Show that f(x) is even

Page 8: 1 When you see… Find the zeros You think…. 2 To find the zeros

8

Even functionEven function

f (-x) = f ( x) y-axis symmetry (example: f(x) = x2)

Page 9: 1 When you see… Find the zeros You think…. 2 To find the zeros

9

You think…

When you see…

Show that f(x) is odd

Page 10: 1 When you see… Find the zeros You think…. 2 To find the zeros

10

Odd functionOdd function

. f ( -x) = - f ( x ) origin symmetry (example: f(x) = x3)

Page 11: 1 When you see… Find the zeros You think…. 2 To find the zeros

11

You think…

When you see…

Find the interval where f(x) is increasing

Page 12: 1 When you see… Find the zeros You think…. 2 To find the zeros

12

ff(x) increasing(x) increasing

Find f ’ (x) = 0 or f ’ (x) = undef

Determine where f ’ (x) > 0 Answer: ( a, b ) or a < x < b

Page 13: 1 When you see… Find the zeros You think…. 2 To find the zeros

13

You think…

When you see…

Find the interval where the slope of f (x) is increasing

Page 14: 1 When you see… Find the zeros You think…. 2 To find the zeros

14

Slope of Slope of f f (x) is increasing(x) is increasing

Find f “ (x)

Set f “ (x) = 0 and f “ (x) = undefined

Make sign chart of f “ (x)

Determine where f “ (x) is positive

Page 15: 1 When you see… Find the zeros You think…. 2 To find the zeros

15

You think…

When you see…

Find the minimum value of a function

Page 16: 1 When you see… Find the zeros You think…. 2 To find the zeros

16

Local Minimum value of a functionLocal Minimum value of a function

Make a sign chart of f ‘( x)

Find x where f ‘( x) changes from - to + Plug those x values into f (x) Choose the smallest

Page 17: 1 When you see… Find the zeros You think…. 2 To find the zeros

17

You think…

When you see…

Find critical numbers

Page 18: 1 When you see… Find the zeros You think…. 2 To find the zeros

18

Find critical numbersFind critical numbers

Find f ‘ (x ) = 0 and f ‘ (x ) = undef.

Page 19: 1 When you see… Find the zeros You think…. 2 To find the zeros

19

You think…

When you see…

Find inflection points

Page 20: 1 When you see… Find the zeros You think…. 2 To find the zeros

20

Find inflection pointsFind inflection points

Find f ‘‘ (x ) = 0 and f ‘‘ (x ) = undef. Make a sign chart of f “ (x) Find where f ‘‘ (x ) changes sign ( + to - ) or ( - to + )

Page 21: 1 When you see… Find the zeros You think…. 2 To find the zeros

21

You think…

When you see…

Show that exists lim ( )x a

f x

Page 22: 1 When you see… Find the zeros You think…. 2 To find the zeros

22

Show existsShow exists lim ( )x a

f x

Show that

limx a

f x limx a

f x

Page 23: 1 When you see… Find the zeros You think…. 2 To find the zeros

23

You think…

When you see…

Show that f(x) is continuous

Page 24: 1 When you see… Find the zeros You think…. 2 To find the zeros

24

..f(x) is continuousf(x) is continuous

S h o w t h a t

1 ) xfax

lim e x i s t s ( p r e v i o u s s l i d e )

2 ) af e x i s t s

3 ) afxfax

lim

Page 25: 1 When you see… Find the zeros You think…. 2 To find the zeros

25

You think…

When you see…

Show that f(x) is differentiable at x = a

Page 26: 1 When you see… Find the zeros You think…. 2 To find the zeros

26

f(x) is differentiablef(x) is differentiable

Show that

1) f(a) is continuous (previous slide) 2) xfxf

axax

limlim

Page 27: 1 When you see… Find the zeros You think…. 2 To find the zeros

27

You think…

When you see…

Find vertical

asymptotes of f(x)

Page 28: 1 When you see… Find the zeros You think…. 2 To find the zeros

28

Find vertical asymptotes of f(x)Find vertical asymptotes of f(x)

Factor/cancel f(x)

Set denominator = 0

Page 29: 1 When you see… Find the zeros You think…. 2 To find the zeros

29

You think…

When you see…

Find horizontal asymptotes of f(x)

Page 30: 1 When you see… Find the zeros You think…. 2 To find the zeros

30

Find horizontal asymptotes of f(x)Find horizontal asymptotes of f(x)

Show

xfx lim

and

xf

x lim

Page 31: 1 When you see… Find the zeros You think…. 2 To find the zeros

31

You think…

When you see…

Find the average rate of change of f(x) at [a, b]

Page 32: 1 When you see… Find the zeros You think…. 2 To find the zeros

32

Average rate of change of f(x)Average rate of change of f(x)

Find

f (b) - f ( a)

b - a

Page 33: 1 When you see… Find the zeros You think…. 2 To find the zeros

33

You think…

When you see…

Find the instantaneous rate of change of f(x)

at x = a

Page 34: 1 When you see… Find the zeros You think…. 2 To find the zeros

34

Instantaneous rate of change of f(x)Instantaneous rate of change of f(x)

Find f ‘ ( a)

Page 35: 1 When you see… Find the zeros You think…. 2 To find the zeros

35

You think…

When you see…

Find the average valueof xf on ba,

Page 36: 1 When you see… Find the zeros You think…. 2 To find the zeros

36

Average value of the functionAverage value of the function

Find b

adxxf

ab)(

1

Page 37: 1 When you see… Find the zeros You think…. 2 To find the zeros

37

You think…

When you see…

Find the absolute maximum of f(x) on [a, b]

Page 38: 1 When you see… Find the zeros You think…. 2 To find the zeros

38

Find the absolute maximum of f(x)Find the absolute maximum of f(x)

a) Make a sign chart of f ’(x) b) Find all x values where relative maxima occur (where f ’(x) changes from + to -) Be sure to check endpoints c) Plug those x values into f (x) d) Choose the largest y value

Page 39: 1 When you see… Find the zeros You think…. 2 To find the zeros

39

You think…

When you see…

Show that a piecewise function is differentiable at the point a where the function rule splits

Page 40: 1 When you see… Find the zeros You think…. 2 To find the zeros

40

Show a piecewise function is Show a piecewise function is

differentiable at x=adifferentiable at x=a

F i r s t , b e s u r e t h a t t h e f u n c t i o n i s c o n t i n u o u s a t

ax .

T a k e t h e d e r i v a t i v e o f e a c h p i e c e a n d s h o w t h a t

xfxfaxax

limlim

Page 41: 1 When you see… Find the zeros You think…. 2 To find the zeros

41

You think…

When you see…

Given s(t) (position function),

find v(t)

Page 42: 1 When you see… Find the zeros You think…. 2 To find the zeros

42

Given position s(t), find v(t)Given position s(t), find v(t)

Find tvts

Page 43: 1 When you see… Find the zeros You think…. 2 To find the zeros

43

You think…

When you see…

Given v(t), find how far a particle travels on [a, b]

Page 44: 1 When you see… Find the zeros You think…. 2 To find the zeros

44

Given v(t), find how far a particle Given v(t), find how far a particle travels on [a,b]travels on [a,b]

think . . . Total

Find b

a

dttv

Page 45: 1 When you see… Find the zeros You think…. 2 To find the zeros

45

You think…

When you see…

Find the average velocity of a particle

on [a, b]

Page 46: 1 When you see… Find the zeros You think…. 2 To find the zeros

46

Find the average rate of change on Find the average rate of change on [a,b][a,b]

Find

abasbs

ab

dttvb

a

Page 47: 1 When you see… Find the zeros You think…. 2 To find the zeros

47

You think…

When you see…

Given v(t), determine if a particle is speeding up at

t = k

Page 48: 1 When you see… Find the zeros You think…. 2 To find the zeros

48

Given v(t), determine if the particle is Given v(t), determine if the particle is speeding up at t=kspeeding up at t=k

Find v(k) and a(k). If v(k) and a(k) signs are the same, the particle is speeding up. If v(k) and a(k) signs are different, the particle is slowing down.

Page 49: 1 When you see… Find the zeros You think…. 2 To find the zeros

49

You think…

When you see…

Given v(t) and s(0),

find s(t)

Page 50: 1 When you see… Find the zeros You think…. 2 To find the zeros

50

Given v(t) and s(0), find s(t)Given v(t) and s(0), find s(t)

dttvsts 0

Page 51: 1 When you see… Find the zeros You think…. 2 To find the zeros

51

You think…

When you see…

Show that the Mean Value Theorem holds

on [a, b]

Page 52: 1 When you see… Find the zeros You think…. 2 To find the zeros

52

Show that the MVT holds on [a,b]Show that the MVT holds on [a,b]

S h o w th a t f is c o n tin u o u s a n d d if fe re n tia b leo n th e in te rv a l .

T h e n f in d s o m e c s u c h th a t

f c f b f a

b a.

Page 53: 1 When you see… Find the zeros You think…. 2 To find the zeros

53

You think…

When you see…

Show that Rolle’s Theorem holds on [a, b]

Page 54: 1 When you see… Find the zeros You think…. 2 To find the zeros

54

Show that Rolle’s Theorem holds on Show that Rolle’s Theorem holds on [a,b][a,b]

Show that f is continuous and differentiableon the interval

If

f af b , then find some c in

a,b such that

f c0.

Page 55: 1 When you see… Find the zeros You think…. 2 To find the zeros

55

You think…

When you see…

Find the domain

of f(x)

Page 56: 1 When you see… Find the zeros You think…. 2 To find the zeros

56

Find the domain of f(x)Find the domain of f(x)

Assume domain is

, . Domain restrictions: non-zero denominators, Square root of non negative numbers, Log or ln of positive numbers

Page 57: 1 When you see… Find the zeros You think…. 2 To find the zeros

57

You think…

When you see…

Find the range

of f(x) on [a, b]

Page 58: 1 When you see… Find the zeros You think…. 2 To find the zeros

58

Find the range of f(x) on [a,b]Find the range of f(x) on [a,b]

Use max/min techniques to find relative maximums and minimums. Then examine f(a), f(b) and endpoints

Page 59: 1 When you see… Find the zeros You think…. 2 To find the zeros

59

You think…

When you see…

Find the range

of f(x) on ( , )

Page 60: 1 When you see… Find the zeros You think…. 2 To find the zeros

60

Use max/min techniques to find relativemax/mins.

Then examine

limx

f x .

Find the range of f(x) onFind the range of f(x) on ,

Page 61: 1 When you see… Find the zeros You think…. 2 To find the zeros

61

You think…

When you see…

Find f ’(x) by definition

Page 62: 1 When you see… Find the zeros You think…. 2 To find the zeros

62

Find f Find f ‘‘( x) by definition( x) by definition

f x limh0

f x h f x h

or

f x limx a

f x f a x a

Page 63: 1 When you see… Find the zeros You think…. 2 To find the zeros

63

You think…

When you see…

Find the derivative of the inverse of f(x) at x = a

Page 64: 1 When you see… Find the zeros You think…. 2 To find the zeros

64

Derivative of the inverse of f(x) at x=aDerivative of the inverse of f(x) at x=a

Interchange x with y.

Find dx

dy implicitly (in terms of y).

Plug your x value into the inverse relation and solve for y.

Finally, plug that y into your dx

dy.

Page 65: 1 When you see… Find the zeros You think…. 2 To find the zeros

65

You think…

When you see…

y is increasing proportionally to y

Page 66: 1 When you see… Find the zeros You think…. 2 To find the zeros

66

.y is increasing proportionally to yy is increasing proportionally to y

kydt

dy

translating to

ktCey

Page 67: 1 When you see… Find the zeros You think…. 2 To find the zeros

67

You think…

When you see…

Find the line x = c that divides the area under

f(x) on [a, b] into two equal areas

Page 68: 1 When you see… Find the zeros You think…. 2 To find the zeros

68

Find the x=c so the area under f(x) is Find the x=c so the area under f(x) is

divided equallydivided equally

dxxfdxxfb

c

c

a

Adxxfc

a 2

1

Page 69: 1 When you see… Find the zeros You think…. 2 To find the zeros

69

You think…

When you see…

dttfdx

d x

a

Page 70: 1 When you see… Find the zeros You think…. 2 To find the zeros

70

Fundamental TheoremFundamental Theorem

2nd FTC: Answer is xf

Page 71: 1 When you see… Find the zeros You think…. 2 To find the zeros

71

You think…

When you see…

m

adttf

dx

d)(

Page 72: 1 When you see… Find the zeros You think…. 2 To find the zeros

72

Fundamental Theorem, againFundamental Theorem, again

2nd FTC. . . Answer is: dx

dmmf

m

adttf

dx

d)(Given:

Page 73: 1 When you see… Find the zeros You think…. 2 To find the zeros

73

You think…

When you see…

The rate of change of population is …

Page 74: 1 When you see… Find the zeros You think…. 2 To find the zeros

74

Rate of change of a population Rate of change of a population

...dt

dP

Page 75: 1 When you see… Find the zeros You think…. 2 To find the zeros

75

You think…

When you see…

The line y = mx + b is tangent to f(x) at (a, b)

Page 76: 1 When you see… Find the zeros You think…. 2 To find the zeros

76

.y = mx+b is tangent to f(x) at (a,b)y = mx+b is tangent to f(x) at (a,b)

Two relationships are true. The two functions share the same slope ( xfm ) and share the same point (a,b)

Page 77: 1 When you see… Find the zeros You think…. 2 To find the zeros

77

You think…

When you see…

Integrate

Page 78: 1 When you see… Find the zeros You think…. 2 To find the zeros

78

1. Estimation:LRAMRRAM (Riemann Sums)MRAMTrapezoid

2. Geometry

3. AntiderivativeStraight ForwardSubstitutionRewrite (Simplify)

Methods for IntegrationMethods for Integration

Page 79: 1 When you see… Find the zeros You think…. 2 To find the zeros

79

You think…

When you see…

Find area using Left Riemann sums

Page 80: 1 When you see… Find the zeros You think…. 2 To find the zeros

80

Area using Left Riemann sumsArea using Left Riemann sums

1210 ... nyyyybaseA

A R t dtz( )

Page 81: 1 When you see… Find the zeros You think…. 2 To find the zeros

81

You think…

When you see…

Find area using Right Riemann sums

Page 82: 1 When you see… Find the zeros You think…. 2 To find the zeros

82

Area using Right Riemann sumsArea using Right Riemann sums

nyyyybaseA ...321

A R t dtz( )

Page 83: 1 When you see… Find the zeros You think…. 2 To find the zeros

83

You think…

When you see…

Find area using Midpoint rectangles

Page 84: 1 When you see… Find the zeros You think…. 2 To find the zeros

84

Area using midpoint rectanglesArea using midpoint rectangles

Typically done with a table of values.

Be sure to use only values that are given.

If you are given 6 sets of points, you can only do 3 midpoint rectangles.

Page 85: 1 When you see… Find the zeros You think…. 2 To find the zeros

85

You think…

When you see…

Find area using trapezoids

Page 86: 1 When you see… Find the zeros You think…. 2 To find the zeros

86

Area using trapezoidsArea using trapezoids

A R t dtz( )

nn yyyyybase

A 1210 2...222

This formula only works when the base is the same. If not, you have to do individual trapezoids.

Page 87: 1 When you see… Find the zeros You think…. 2 To find the zeros

87

You think…

When you see…

Solve the differential equation …

Page 88: 1 When you see… Find the zeros You think…. 2 To find the zeros

88

Solve the differential equation...Solve the differential equation...

Separate the variables – x on one side, y on the other. Separate only by multiplication or division and the dx and dy must all be upstairs..

Page 89: 1 When you see… Find the zeros You think…. 2 To find the zeros

89

You think…

When you see…

Meaning of

dttfx

a

Page 90: 1 When you see… Find the zeros You think…. 2 To find the zeros

90

Meaning of the integral of f(t) from a to xMeaning of the integral of f(t) from a to x

The accumulation function –

accumulated area under the function xf

starting at some constant a and ending at x

Page 91: 1 When you see… Find the zeros You think…. 2 To find the zeros

91

You think…

When you see…

Given a base, cross sections perpendicular to

the x-axis that are squares

Page 92: 1 When you see… Find the zeros You think…. 2 To find the zeros

92

Semi-circular cross sections Semi-circular cross sections perpendicular to the x-axisperpendicular to the x-axis

The area between the curves typically is the base of your square.

dxbaseVb

a

2

Page 93: 1 When you see… Find the zeros You think…. 2 To find the zeros

93

You think…

When you see…

Find where the tangent line to f(x) is horizontal

Page 94: 1 When you see… Find the zeros You think…. 2 To find the zeros

94

Horizontal tangent lineHorizontal tangent line

Set xf = 0

Page 95: 1 When you see… Find the zeros You think…. 2 To find the zeros

95

You think…

When you see…

Find where the tangent line to f(x) is vertical

Page 96: 1 When you see… Find the zeros You think…. 2 To find the zeros

96

Vertical tangent line to f(x)Vertical tangent line to f(x)

Find xf . Set the denominator equal to zero.

Page 97: 1 When you see… Find the zeros You think…. 2 To find the zeros

97

You think…

When you see…

Find the minimum

acceleration given v(t)

Page 98: 1 When you see… Find the zeros You think…. 2 To find the zeros

98

Given v(t), find minimum accelerationGiven v(t), find minimum acceleration

First find the acceleration tatv Minimize the acceleration by

Setting ta = 0 or ta = undef. Then determine where ta changes

from – to +

Page 99: 1 When you see… Find the zeros You think…. 2 To find the zeros

99

You think…

When you see…

Approximate the value f(0.1) of by using the

tangent line to f at x = a

Page 100: 1 When you see… Find the zeros You think…. 2 To find the zeros

100

Approximate f(0.1) using tangent line Approximate f(0.1) using tangent line to f(x) at x = 0to f(x) at x = 0

Find the equation of the tangent line to f using 11 xxmyy where afm and the point is afa, . Then plug in 0.1 into x and solve for y.

Be sure to use an approximation sign.

Page 101: 1 When you see… Find the zeros You think…. 2 To find the zeros

101

You think…

When you see…

Given the value of F(a) and the fact that the

anti-derivative of f is F, find F(b)

Page 102: 1 When you see… Find the zeros You think…. 2 To find the zeros

102

Given Given FF((aa)) and the that the and the that the anti-derivative of anti-derivative of ff is is FF, find , find FF((bb))

Usually, this problem contains an antiderivative you cannot take. Utilize the fact that if xF is the antiderivative of f,

then aFbFdxxfb

a

.

Solve for bF using the calculator to find the definite integral

Page 103: 1 When you see… Find the zeros You think…. 2 To find the zeros

103

You think…

When you see…

Find the derivative off(g(x))

Page 104: 1 When you see… Find the zeros You think…. 2 To find the zeros

104

Find the derivative of f(g(x))Find the derivative of f(g(x))

xgxgf

Think . . . Chain Rule

Page 105: 1 When you see… Find the zeros You think…. 2 To find the zeros

105

You think…

When you see…

Given , find dxxfb

a

dxkxfb

a

Page 106: 1 When you see… Find the zeros You think…. 2 To find the zeros

106

Given area under a curve and vertical Given area under a curve and vertical shift, find the new area under the curveshift, find the new area under the curve

dxkdxxfdxkxfb

a

b

a

b

a

Page 107: 1 When you see… Find the zeros You think…. 2 To find the zeros

107

You think…

When you see…

Given a graph of

find where f(x) is

increasing

'( )f x

Page 108: 1 When you see… Find the zeros You think…. 2 To find the zeros

108

Given a graph of f ‘(x) , find where f(x) is Given a graph of f ‘(x) , find where f(x) is increasingincreasing

Make a sign chart of xf

Determine where xf is positive

Page 109: 1 When you see… Find the zeros You think…. 2 To find the zeros

109

You think…

When you see…

Given v(t) and s(0), find the greatest distance from the origin of a particle on [a, b]

Page 110: 1 When you see… Find the zeros You think…. 2 To find the zeros

110

Given Given vv((tt)) and and ss(0)(0), find the greatest distance from , find the greatest distance from the origin of a particle on [the origin of a particle on [aa, , bb]]

Generate a sign chart of tv to find turning points.Integrate tv using 0s to find the constant to find ts .Find s(all turning points) which will giveyou the distance from your starting point.

Adjust for the origin.

Page 111: 1 When you see… Find the zeros You think…. 2 To find the zeros

111

When you see…

Given a water tank with g gallons initially being filled at the rate of F(t) gallons/min and emptied at the rate of E(t) gallons/min on

, find

1,0 t

Page 112: 1 When you see… Find the zeros You think…. 2 To find the zeros

112

You think…

a) the amount of water in

the tank at m minutes

Page 113: 1 When you see… Find the zeros You think…. 2 To find the zeros

113

Page 114: 1 When you see… Find the zeros You think…. 2 To find the zeros

114

Amount of water in the tank at t minutesAmount of water in the tank at t minutes

dttEtFt

1

0

initial gallons

Page 115: 1 When you see… Find the zeros You think…. 2 To find the zeros

115

You think…

b) the rate the water

amount is changing

at m

Page 116: 1 When you see… Find the zeros You think…. 2 To find the zeros

116

Rate the amount of water is changing at t = m

mEmFdttEtFdt

d m

t

Page 117: 1 When you see… Find the zeros You think…. 2 To find the zeros

117

You think…

c) the time when the

water is at a minimum

Page 118: 1 When you see… Find the zeros You think…. 2 To find the zeros

118

The time when the water is at a minimumThe time when the water is at a minimum

mEmF = 0,

testing the endpoints as well.

Page 119: 1 When you see… Find the zeros You think…. 2 To find the zeros

119

You think…

When you see…

Given a chart of x and f(x) on selected values between a and b, estimate where c is between a and b.

'( )f x

Page 120: 1 When you see… Find the zeros You think…. 2 To find the zeros

120

Straddle c, using a value k greater than c and a value h less than c.

so hk

hfkfcf

Page 121: 1 When you see… Find the zeros You think…. 2 To find the zeros

121

You think…

When you see…

Given , draw a

slope field dx

dy

Page 122: 1 When you see… Find the zeros You think…. 2 To find the zeros

122

Draw a slope field of dy/dxDraw a slope field of dy/dx

Use the given points

Plug them into dx

dy,

drawing little lines with theindicated slopes at the points.

Page 123: 1 When you see… Find the zeros You think…. 2 To find the zeros

123

You think…

When you see…

Find the area between curves f(x) and g(x) on

[a,b]

Page 124: 1 When you see… Find the zeros You think…. 2 To find the zeros

124

Area between f(x) and g(x) on [a,b]Area between f(x) and g(x) on [a,b]

dxxgxfAb

a ,

assuming f (x) > g(x)

Page 125: 1 When you see… Find the zeros You think…. 2 To find the zeros

125

You think…

When you see…

Find the volume if the area between the curves f(x) and g(x)

with a representative rectangle perpendicular to the axis of rotation

Page 126: 1 When you see… Find the zeros You think…. 2 To find the zeros

126

Volume generated by rotating area between Volume generated by rotating area between f(x) and g(x) with a representative rectangle f(x) and g(x) with a representative rectangle

perpendicularperpendicular to the axis of rotation to the axis of rotation

dxrRVb

a 22

Page 127: 1 When you see… Find the zeros You think…. 2 To find the zeros

127

You think…

When you see…

Find the volume if the area between the curves f(x) and g(x)

with a representative rectangle parallel to the axis of rotation

Page 128: 1 When you see… Find the zeros You think…. 2 To find the zeros

128

Volume generated by rotating area between Volume generated by rotating area between f(x) and g(x) with a representative rectangle f(x) and g(x) with a representative rectangle

parallelparallel to the axis of rotation to the axis of rotation

dxrectaxisxVb

a 2

Remember: Always . . . Big - small