Homework, Page 366
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Transcript of Homework, Page 366
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Homework, Page 366
Find the values of all six trigonometric functions of the angle x.
1.5 4
3
x
4 3 4sin ;cos ; tan
5 5 35 5 3
csc ;sec ;cot4 3 4
x x x
x x x
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Homework, Page 366Find the values of all six trigonometric functions of the angle x.
5.
2 2 2 27 11 150 5 6
7 7 6 11 11 6 7sin ;cos ; tan
30 30 115 6 5 6
5 6 5 6 11csc ;sec ;cot
7 11 7
c a b
x x x
x x x
7
11
x
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Homework, Page 366Assume that θ is an acute angle in a right triangle satisfying the given condition. Evaluate the remaining trigonometric functions.
9. 3sin
7
2 23sin 49 9 2 10
7
2 10 3 3 10cos ; tan
7 202 10
7 7 7 10 2 10csc ;sec ;cot
3 20 32 10
a c b
x
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Homework, Page 366Assume that θ is an acute angle in a right triangle satisfying the given condition. Evaluate the remaining trigonometric functions.
13. 5tan
9
2 25tan 25 81 106
9
5 5 106 9 3 106sin ;cos
106 106106 106
106 106 9csc ;sec ;cot
5 9 5
c a b
x
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Homework, Page 366Assume that θ is an acute angle in a right triangle satisfying the given condition. Evaluate the remaining trigonometric functions.
17. 23csc
9
2 223csc 529 81 448 8 7
9
9 8 7 9 9 7sin ;cos ; tan
23 23 568 7
23 23 7 8 7sec ;cot
56 98 7
a c b
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Homework, Page 366Evaluate without using a calculator.
21. cot6
3cos6 2cot 3
16sin
26
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Homework, Page 366Evaluate using a calculator. Given an exact value.
25. sec45
1 2 2 2sec45 2
22 2
2
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Homework, Page 366Evaluate using a calculator, giving answers to three decimal places.
29. sin 74sin 74 0.961
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Homework, Page 366Evaluate using a calculator, giving answers to three decimal places.
33. tan12
tan 0.26812
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Homework, Page 366Evaluate using a calculator, giving answers to three decimal places.
37. cot 0.89cot 0.89 0.810
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Homework, Page 366Without a calculator, find the acute angle θ that satisfies the equation. Give θ in both degrees and radians.
41. 1sin
2
1sin 30
2 6
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Homework, Page 366Without a calculator, find the acute angle θ that satisfies the equation. Give θ in both degrees and radians.
45. sec 2
1sec 2 cos 60
2 3
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Homework, Page 366Solve for the variable shown.
49.
15 15sin34 26.824
sin34x
x
x15
34
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Homework, Page 366Solve for the variable shown.
53.
6 6sin35 10.461
sin35y
y
6
35
y
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Homework, Page 366Solve for the variable shown.
57.55 15.58a
x
y
a
b
c
55 15.58 cos 27.163cos
35 tan tan 22.251
a aa c
c
bb a
a
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Homework, Page 36661. A guy wire from the top of a radio tower forms a 75º angle with the ground at a 55 ft distance from the foot of the tower. How tall is the tower?
75 55 tan
tan 55 tan 75 205.263 ft
ba
a
b a
55
75
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Homework, Page 36665. A surveyor wanted to measure the length of a lake. Two assistants, A and C, positioned themselves at opposite ends of the lake and the surveyor positioned himself 100 feet perpendicular to the line between the assistants and on the perpendicular line from the assistant C. If the angle between his lines of sight to the two assistants is 79º12‘42“, what is the length of the lake?
75 12 42 tan100
42 12.775 12 42 75 12 75 75.212
60 60
100 tan 75 12 42 378.797 ft
AC AC
BC
AC
75 12' 42"
100
ft
A C
B
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Homework, Page 36669. Which of the following expressions does not
represent a real number?
a. sin 30º
b. tan 45º
c. cod 90º
d. csc 90º
e. sec 90º
1
1
sin30 0.5; tan 45 1
cos90 0;csc90 1
csc90 0
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Homework, Page 36673. The table is a simplified trig table. Which column is the values for the sine, the cosine, and the tangent functions?
The second column is tangent values, because tangent can be greater than one, the third is sine values, because they are increasing and the fourth column is cosine values because they are decreasing.
Angle ? ? ?
40º 0.8391 0.6428 0.7660
42 º 0.9004 0.6691 0.7431
44 º 0.9657 0.6047 0.7191
46 º 1.0355 0.7191 0.6047
48 º 1.1106 0.7431 0.6691
50 º 1.1917 0.7660 0.6428
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4.3
Trigonometry Extended: The Circular Functions
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What you’ll learn about
Trigonometric Functions of Any Angle Trigonometric Functions of Real Numbers Periodic Functions The 16-point unit circle
… and whyExtending trigonometric functions beyond triangle ratios opens up a new world of applications.
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Leading Questions
We may substitute any real number n for θ in any trig function and find the value of the function.Cosine is negative in the fourth quadrant.Coterminal angles have the same measure.Quadrantal angles have their terminal sides in the center of the quadrants.The period of a trig function tells us how often it takes on identical values.
Slide 4- 22
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Initial Side, Terminal Side
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Positive Angle, Negative Angle
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Coterminal Angles
Two angles in an extended angle-measurement system can have the same initial side and the same terminal side, yet have different measures. Such angles are called coterminal angles.
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Example Finding Coterminal Angles
Find a positive angle and a negative angle that are coterminal
with 45 .
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Example Finding Coterminal Angles
Find a positive angle and a negative angle that are coterminal
with .6
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Example Evaluating Trig Functions Determined by a Point in Quadrant I
Let be the acute angle in standard position whose terminal
side contains the point (3,5). Find the six trigonometric functions
of .
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Trigonometric Functions of any Angle
2 2
Let be any angle in standard position and let ( , )
be any point on the terminal side of the angle (except
the origin). Let denote the distance from ( , ) to
the origin, i.e., let . Then
P x y
r P x y
r x y
sin csc ( 0)
cos sec ( 0)
tan ( 0) cot ( 0)
y ry
r y
x rx
r xy x
x yx y
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Evaluating Trig Functions of a Nonquadrantal Angle θ
1. Draw the angle θ in standard position, being careful to place the terminal side in the correct quadrant.
2. Without declaring a scale on either axis, label a point P (other than the origin) on the terminal side of θ.
3. Draw a perpendicular segment from P to the x-axis, determining the reference triangle. If this triangle is one of the triangles whose ratios you know, label the sides accordingly. If it is not, then you will need to use your calculator.
4. Use the sides of the triangle to determine the coordinates of point P, making them positive or negative according to the signs of x and y in that particular quadrant.
5. Use the coordinates of point P and the definitions to determine the six trig functions.
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Signs of Trigonometric Functions
Slide 4- 31
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Reference Angles
The acute angle made by the terminal side of an angle and the x-axis is called the reference angle.
The absolute value of each trig function is equal to the absolute value of the same trig function of the reference angle in the first quadrant. The sign of the trig function is determined by the quadrant in which the terminal side lies.
Slide 4- 32
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Example Evaluating More Trig Functions
Find sin 210 without a calculator.
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Example Using one Trig Ratio to Find the Others
Find sin and cos , given tan 4 / 3 and cos 0.
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Unit Circle
The unit circle is a circle of radius 1 centered at the origin.
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Trigonometric Functions of Real NumbersLet be any real number, and let ( , ) be the point
corresponding to when the number line is wrapped
onto the unit circle as described above. Then
1sin csc ( 0)
cos
t P x y
t
t y t yy
t x
1
sec ( 0)
tan ( 0) cot ( 0)
t xx
y xt x t yx y
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Periodic Function
A function ( ) is if there is a positive number such that
( ) ( ) for all values of in the domain of . The smallest such
number is called the of the function.
y f t c
f t c f t t f
c
periodic
period
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The 16-Point Unit Circle
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Following Questions
Graphs of the sine function may be stretched vertically, but not horizontally.
Horizontal stretches of the cosine function are the result of changes in its period.
Horizontal translations of the sine function are the result of phase shifts.
Sinusoids are functions whose graphs have the shape of the sine curve.
Sinusoids may be used to model periodic behavior.
Slide 4- 39
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Homework
Homework Assignment #28 Review Section 4.3 Page 381, Exercises: 1 – 69 (EOO) Quiz next time
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4.4
Graphs of Sine and Cosine: Sinusoids
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Quick Review
1
State the sign (positive or negative) of the function in each quadrant.
1. sin
2. cot
Give the radian measure of the angle.
3. 150
4. 135
5. Find a transformation that will transform the graph of
x
x
y
2
to
the graph of 2 .
x
y x
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Quick Review Solutions
+,+, ,
+, ,+
State the sign (positive or negative) of the function in each quadrant.
1. sin
2. cot
Give the radian measure of the angle.
3. 150
,
5 /6
3 /4
4. 135
5. Find a transformation th
x
x
1
2
at will transform the graph of to
the vertgr icaph allyof 2 stretch by 2.
y x
y x
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What you’ll learn about
The Basic Waves Revisited Sinusoids and Transformations Modeling Periodic Behavior with Sinusoids
… and why
Sine and cosine gain added significance when
used to model waves and periodic behavior.
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Sinusoid
A function is a if it can be written in the form
( ) sin( ) where , , , and are constants
and neither nor is 0.
f x a bx c d a b c d
a b
sinusoid
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Amplitude of a Sinusoid
The of the sinusoid ( ) sin( ) is | |.
Similarly, the amplitude of ( ) cos( ) is | |.
Graphically, the amplitude is half the distance between the
trough and the crest of the wave
f x a bx c d a
f x a bx c d a
amplitude
.
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Example Finding Amplitude
Find the amplitude of each function and use the language of transformations to describe how the graphs are related.
(a) (b) (c) 1 siny x 2 2siny x 1
1sin
3y x
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Period of a Sinusoid
The of the sinusoid ( ) sin( ) is
2 / | | . Similarly, the period of ( ) cos( )
is 2 / | | . Graphically, the period is the length of one
full cycle of the wave.
p f x a bx c d
p b f x a bx c d
p b
period
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Example Finding Period and Frequency
Find the period and frequency of each function and use the language of transformations to describe how the graphs are related.
(a) (b) (c) 1 siny x 2 2sin 2y x 1 3sin3
xy
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Example Horizontal Stretch or Shrink and Period
Find the period of sin and use the language of 2
transformations to describe how the graph relates to
sin .
xy
y x
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Frequency of a Sinusoid
The of the sinusoid ( ) sin( )
is | | / 2 1 . Similarly, the frequency of
( ) cos( ) is | | / 2 1 . Graphically,
the frequency is the number of complete cycles the wave
c
f f x a bx c d
f b p
f x a bx c d f b p
frequency
ompletes in a unit interval.
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Example Combining a Phase Shift with a Period Change
Construct a sinusoid with period /3 and amplitude 4
that goes through (2,0).
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Graphs of Sinusoids The graphs of sin( ( )) and cos( ( ))
(where 0 and 0) have the following characteristics:
amplitude = | | ;
2period = ;
| |
| |frequency = .
2When complared to the graphs of sin and
y a b x h k y a b x h k
a b
a
b
b
y a bx
cos ,
respectively, they also have the following characteristics:
a phase shift of ;
a vertical translation of .
y a bx
h
k
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Constructing a Sinusoidal Model using Time
1. Determine the maximum value and minimum value .
The amplitude of the sinusoid will be , and 2
the vertical shift will be .2
2. Determine the period , the time interval of a single cy
M m
M mA A
M mC
p
cle
of the periodic function. The horizontal shrink (or stretch)
2will be .B
p
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Constructing a Sinusoidal Model using Time
3. Choose an appropriate sinusoid based on behavior
at some given time . For example, at time :
( ) cos( ( )) attains a maximum value;
( ) cos( ( )) attains a minimum value;
( ) sin( (
T T
f t A B t T C
f t A B t T C
f t A B t
)) is halfway between a minimum
and a maximum value;
( ) sin( ( )) is halfway between a maximum
and a minimum value.
T C
f t A B t T C
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Example Constructing a Sinusoidal Model
On a certain day, high tide occurs at 7:12 AM and the
water depth is measured at 15 ft. On the same day, low
tide occurs at 1:24 and the water depth measures 8 ft.
(a) Write a sinusoidal function modeling the tide.
(b) What is the approximate depth of water at 11:00 AM?
At 3:00 PM?
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Example Constructing a Sinusoidal Model
(c) At what time did the first low tide occur? The second
high tide?