Lesson 12
NYS COMMON CORE MATHEMATICS CURRICULUM
M4
PRECALCULUS AND ADVANCED TOPICS
Lesson 12: Inverse Trigonometric Functions
Student Outcomes

Students understand that restricting a trigonometric function to a domain on which it is always increasing or
always decreasing allows its inverse to be constructed.

Students use inverse functions to solve trigonometric equations.
Lesson Notes
Students studied inverse functions in Module 3 and came to the realization that not every function has an inverse that is
also a function. Students considered how to restrict the domain of a function to produce an invertible function
(F-BF.B.4d). This lesson builds on that understanding of inverse functions by restricting the domains of the trigonometric
functions in order to develop the inverse trigonometric functions (F-TF.B.6). In Geometry, students used arcsine,
arccosine, and arctangent to find missing angles, but they did not understand inverse functions and, therefore, did not
use the terminology or notation for inverse trigonometric functions. Students define the inverse trigonometric functions
in this lesson. Then they use the notation sin−1 (𝑥) rather than arcsin(𝑥). The focus shifts to using the inverse
trigonometric functions to solve trigonometric equations (F-TF.B.7).
Classwork
Opening Exercise (5 minutes)
Give students time to work on the Opening Exercise independently. Then have them compare answers with a partner
before sharing as a class.
Opening Exercise
Use the graphs of the sine, cosine, and tangent functions to answer each of the following questions.
a.
State the domain of each function.
The domain of the sine and cosine functions is the set of all real numbers. The domain of the tangent function
𝝅
is the set of all real numbers 𝒙 ≠ + 𝒌𝝅 for all integers 𝒌.
𝟐
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NYS COMMON CORE MATHEMATICS CURRICULUM
M4
PRECALCULUS AND ADVANCED TOPICS
b.
Scaffolding:
Would the inverse of the sine, cosine, or tangent functions also be functions?
Explain.
If students need a review of
inverse functions, use this
exercise:
None of these functions are invertible. Multiple elements of the domain are paired
with a single range element. When the domain and range are exchanged to form the
inverse, the result will not satisfy the definition of a function.
c.
Consider the function 𝑓(𝑥) =
√𝑥 − 4, which is graphed
below. Graph 𝑓 −1 . Find the
equation of the inverse and its
domain.
For each function, select a suitable domain that will make the function invertible.
Answers will vary so share a variety of responses. Any answer is suitable as long as
the restricted domain leaves an interval of the graph that is either always increasing
or always decreasing.
MP.7
Sample response:
𝝅
𝒚 = sin(𝒙), 𝑫: [𝟎, ]
𝟐

𝒚 = cos(𝒙), 𝑫: [𝟎, 𝝅]
𝝅
𝒚 = 𝐭𝐚𝐧(𝒙), 𝑫: [𝟎, ]
𝟐
Are any of the trigonometric functions invertible?

No. The inverses of the trigonometric functions are no longer functions.
If necessary, remind students of the definition of an invertible function.
INVERTIBLE FUNCTION: The domain of a function 𝑓 can be restricted to make it invertible so that its inverse is also a
function. A function is said to be invertible if its inverse is also a function.

Was there only one way to restrict the domain to make each function invertible?


No. There are an infinite number of ways in which we could restrict the domain of each function.
We just need to erase enough of the graph to where the function is either only increasing or only
decreasing.
How much of the graph should we keep?

We want to choose the largest subset of the domain of the function (such as 𝑓(𝑥) = sin(𝑥)) as we can
and still have the function be continuously increasing or continuously decreasing on that interval.
Ask students to share the domain restriction they chose for each of the three functions. Then, point out that while there
is more than one way to do this, the convention is to use an interval that contains zero.

𝜋
2
𝜋
2
Based on this, the convention is to restrict the domain of 𝑓(𝑥) = sin(𝑥) to be − ≤ 𝑥 ≤ . Does this satisfy
all of our requirements?


Would this same restriction work for 𝑓(𝑥) = cos(𝑥)?


No. The graph would contain an interval of increasing and an interval of decreasing and still would not
be invertible.
If we want to include zero and keep the largest subset of the domain possible, what would be a logical way to
restrict the domain of 𝑓(𝑥) = cos(𝑥) ?


Yes. The graph is entirely increasing. We kept as much of the domain as possible, and we included zero
in the domain.
Either 0 ≤ 𝑥 ≤ 𝜋 or −𝜋 ≤ 𝑥 ≤ 0.
The convention is to restrict the domain of 𝑓(𝑥) = cos(𝑥) to 0 ≤ 𝑥 ≤ 𝜋.
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Date:
Inverse Trigonometric Functions
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Lesson 12
NYS COMMON CORE MATHEMATICS CURRICULUM
M4
PRECALCULUS AND ADVANCED TOPICS

If we want to include zero and keep the largest subset of the domain possible, what would be a logical way to
restrict the domain of 𝑓(𝑥) = tan(𝑥) ?

We could restrict the domain to values from 0 to 𝜋, but we would have to exclude
𝜋
2
from the domain. If
𝜋
2
𝜋
2
we want to keep one branch of the graph and include 0, we should restrict the domain to − < 𝑥 < .

𝜋
2
𝜋
2
The convention is to restrict the domain of 𝑓(𝑥) = tan(𝑥) to − < 𝑥 < .
Example 1 (6 minutes)
Allow students time to read through the example and answer part (a). Then discuss part (b) as a class.

How can we find the equation of the inverse sine?
Write the following on the board.
𝑥 = sin(𝑦)

Now what? We need a function that denotes that it is the inverse of the sine function. The inverse sine
function is usually written as 𝑦 = sin−1 (𝑥). Why does this notation make sense for an inverse function?
The notation 𝑓 −1 (𝑥) means the inverse function of 𝑥, so it makes sense that sin−1 (𝑥) means the
inverse of sine.


𝜋
6
What is the value of sin ( )? What about sin (
1


Both equal .
2
1
2
What is the value of sin−1 ( ) ?
𝜋


5𝜋
)?
6
Why

6
𝜋
6
and not
5𝜋
6
?
𝜋
2
𝜋
2
The range of the inverse sine function is restricted to − ≤ 𝑦 ≤ , which means that while there are an
infinite number of possible answers, there is only one answer that lies within this restricted interval.

What is the value of sin (


1
2
1
2
What is the value of sin−1 (− ) ?


−
11𝜋
)?
6
−
𝜋
6
Would it be acceptable to give the answer as

No.
11𝜋
6
11𝜋
6
?
𝜋
is greater than .
Lesson 12:
Date:
2
Inverse Trigonometric Functions
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Lesson 12
NYS COMMON CORE MATHEMATICS CURRICULUM
M4
PRECALCULUS AND ADVANCED TOPICS

Why is it important for the inverse of sine to be a function?
1
2
1
2
Otherwise there would be an infinite number of possible values of sin−1 ( ). sin−1 ( ) could be any

1
2
value 𝑦 such that sin(𝑦) = . Within the restricted range, there is only one value of 𝑦 that satisfies the
equation.
Scaffolding:
Example 1
Consider the function (𝒙) = 𝐬𝐢𝐧 (𝒙), −
a.
If students need additional practice,
consider using a rapid whiteboard exchange
where you present a problem such as the
examples listed and students hold up their
answer on a small whiteboard. In this way,
you can quickly assess student
understanding.
𝝅
𝝅
≤𝒙≤ .
𝟐
𝟐
State the domain and range of this function.
𝑫: −
𝝅
𝝅
≤𝒙≤
𝟐
𝟐
𝑹: − 𝟏 ≤ 𝒚 ≤ 𝟏
b.
sin−1 (
Find the equation of the inverse function.
𝒙 = 𝐬𝐢𝐧(𝒚)
c.
𝜋
√2
)=
2
4
sin−1 (−
𝜋
√2
)=
2
4
cos −1 (−
𝒚 = 𝐬𝐢𝐧−𝟏 (𝒙)
cos −1 (
State the domain and range of the inverse.
sin−1 (0) = 0
𝑫: − 𝟏 ≤ 𝒙 ≤ 𝟏
tan−1 (
𝝅
𝝅
𝑹: − ≤ 𝒚 ≤
𝟐
𝟐
𝜋
√3
)=
3
6
𝜋
√2
)=−
2
4
3𝜋
√2
)=
2
4
𝜋
cos −1 (0) =
2
𝜋
√3
tan−1 (− ) = −
3
6
If students are struggling, use a unit circle
diagram to assist them in evaluating these
expressions.
Exercises 1–3 (8 minutes)
In these exercises, students are familiarizing themselves with the inverse
trigonometric functions. Give students time to work through the exercises
either individually or in pairs before sharing answers as a class.
Exercises 1–3
1.
Write an equation for the inverse cosine function, and state its domain and
range.
a.
𝒚 = 𝐜𝐨𝐬 −𝟏 (𝒙)
2.
𝑫: − 𝟏 ≤ 𝒙 ≤ 𝟏
𝑹: 𝟎 ≤ 𝒚 ≤ 𝝅
Write an equation for the inverse tangent function, and state its domain and range.
𝒚 = 𝐭𝐚𝐧−𝟏 (𝒙)
Lesson 12:
Date:
𝑫: set of all real numbers
𝑹: −
𝝅
𝝅
<𝒚<
𝟐
𝟐
Inverse Trigonometric Functions
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M4
Lesson 12
NYS COMMON CORE MATHEMATICS CURRICULUM
PRECALCULUS AND ADVANCED TOPICS
3.
Evaluate each of the following expressions without using a calculator. Use radian measures.
a.
√𝟑
𝐬𝐢𝐧−𝟏 (
𝟐
)
𝐬𝐢𝐧−𝟏 (−
b.
𝝅
𝟑
c.
√𝟑
𝟐
)
𝝅
−
𝟑
√𝟑
𝐜𝐨𝐬 −𝟏 (
𝟐
)
𝐜𝐨𝐬 −𝟏 (−
d.
𝝅
𝟔
√𝟑
𝟐
)
𝟓𝝅
𝟔
MP.7
e.
𝐬𝐢𝐧−𝟏 (𝟏)
𝝅
𝟐
f.
𝐬𝐢𝐧−𝟏 (−𝟏)
𝝅
−
𝟐
g.
𝐜𝐨𝐬 −𝟏 (𝟏)
h.
𝐜𝐨𝐬 −𝟏 (−𝟏)
𝟎
i.

𝐭𝐚𝐧−𝟏 (−𝟏)
𝝅
−
𝟒
j.
Because the input is the value of cosine, and the values of cosine range
from −1 to 1.
Why is the range of the inverse cosine function restricted to values from 0 to 𝜋?


𝐭𝐚𝐧−𝟏 (𝟏)
𝝅
𝟒
Why is the domain of the inverse cosine function restricted to values from
−𝟏 to 𝟏?


𝝅
Because we restricted the domain of the cosine function to only the
values from 0 to 𝜋 in order to make it an invertible function. The domain
of the cosine function became the range of the inverse cosine function.
What does this restriction mean in terms of evaluating an inverse trigonometric
function?

The answer must lie within the restricted values of the range.
Scaffolding:
Pose this question to students
who like a challenge:
Does sin(sin−1 (𝑥)) = 𝑥 for all
values of 𝑥?
Yes, for all values in the domain
of sin−1 (𝑥) (−1 ≤ 𝑥 ≤ 1)
Does sin−1 (sin(𝑥)) = 𝑥 for all
values of 𝑥?
No, only for values of 𝑥 such
𝜋
𝜋
that − ≤ 𝑥 ≤ .
2
2
Example 2 (6 minutes)
Work through the examples as a class.

What is the difference between solving the equation cos(𝑥) =

MP.6
1
2
1
1
and evaluating the expression cos −1 ( ) ?
2
2
When solving the equation cos(𝑥) = , we are looking for all values of 𝑥 within the interval
1
2
1
2
0 ≤ 𝑥 ≤ 2𝜋 such that cos(𝑥) = . When evaluating cos −1 ( ), we are looking for the one value within
𝜋
2
the interval− ≤ 𝑦 ≤
Lesson 12:
Date:
𝜋
1
such that cos(𝑦) = .
2
2
Inverse Trigonometric Functions
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Lesson 12
NYS COMMON CORE MATHEMATICS CURRICULUM
M4
PRECALCULUS AND ADVANCED TOPICS

In part (b), why do we find the inverse sine of


2
3
2
3
instead of − ?
We are looking for the reference angle, which is a positive, acute measure in order to find the other
solutions.
When do we need a calculator to find the reference angle?

𝜋 𝜋
𝜋
6 4
3
When we are dealing with a value that is not a multiple of , , or
or on the 𝑥- or 𝑦-axis.
Example 2
Solve each trigonometric equation such that 𝟎 ≤ 𝒙 ≤ 𝟐𝝅. Round to three decimal places when necessary.
a.
𝟐cos(𝒙) − 𝟏 = 𝟎
𝐜𝐨𝐬(𝒙) =
𝟏
𝟐
𝟏
𝟐
Reference angle = 𝐜𝐨𝐬 −𝟏 ( ) =
𝝅
𝟑
The cosine function is positive in Quadrants I and IV.
𝒙=
b.
𝟓𝝅
𝝅
and
𝟑
𝟑
𝟑 sin(𝒙) + 𝟐 = 𝟎
𝐬𝐢𝐧(𝒙) = −
𝟐
𝟑
𝟐
𝟑
Reference angle = 𝐬𝐢𝐧−𝟏 ( ) = 𝟎. 𝟕𝟑𝟎
The sine function is negative in Quadrants III and IV.
𝒙 = 𝝅 + 𝟎. 𝟕𝟑𝟎 = 𝟑. 𝟖𝟕𝟏 and 𝒙 = 𝟐𝝅 − 𝟎. 𝟕𝟑𝟎 = 𝟓. 𝟓𝟓𝟑
Exercises 4–8 (12 minutes)
Give students time to work through the exercises either individually or in pairs. Circulate the room to ensure students
understand the process of solving a trigonometric equation. For Exercises 7–8, consider using a graphing utility to either
solve the equations or to check solutions calculated manually.
Exercises 4–8
4.
Solve each trigonometric equation such that 𝟎 ≤ 𝒙 ≤ 𝟐𝝅. Give answers in exact form.
a.
√𝟐𝐜𝐨𝐬(𝒙) + 𝟏 = 𝟎
𝒙=
b.
𝟑𝝅 𝟓𝝅
,
𝟒 𝟒
𝐭𝐚𝐧(𝒙) − √𝟑 = 𝟎
𝒙=
𝝅 𝟒𝝅
,
𝟑 𝟑
Lesson 12:
Date:
Inverse Trigonometric Functions
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NYS COMMON CORE MATHEMATICS CURRICULUM
M4
PRECALCULUS AND ADVANCED TOPICS
c.
𝐬𝐢𝐧𝟐 (𝒙) − 𝟏 = 𝟎
𝒙=
5.
𝝅 𝟑𝝅
,
𝟐 𝟐
Solve each trigonometric equation such that 𝟎 ≤ 𝒙 ≤ 𝟐𝝅. Round answers to three decimal places.
a.
𝟓 𝐜𝐨𝐬(𝒙) − 𝟑 = 𝟎
𝒙 = 𝟎. 𝟗𝟐𝟕, 𝟓. 𝟑𝟓𝟔
b.
𝟑 cos(𝒙) + 𝟓 = 𝟎
There are no solutions to this equation within the domain of the function.
c.
𝟑 𝐬𝐢𝐧(𝒙) − 𝟏 = 𝟎
𝒙 = 𝟎. 𝟑𝟒𝟎, 𝟐. 𝟖𝟎𝟐
d.
𝐭𝐚𝐧(𝒙) = −𝟎. 𝟏𝟏𝟓
𝒙 = 𝟑. 𝟎𝟐𝟕, 𝟔. 𝟏𝟔𝟗
6.
A particle is moving along a straight line for 𝟎 ≤ 𝒕 ≤ 𝟏𝟖. The velocity of the particle at time 𝒕 is given by the
𝝅
𝟓
function 𝒗(𝒕) = 𝐜𝐨𝐬 ( 𝒕). Find the time(s) on the interval 𝟎 ≤ 𝒕 ≤ 𝟏𝟖 where the particle is at rest (𝒗(𝒕) = 𝟎).
The particle is at rest at 𝒕 = 𝟐. 𝟓, 𝟕. 𝟓, 𝟏𝟐. 𝟓, and 𝟏𝟕.
7.
In an amusement park, there is a small Ferris wheel, called a kiddie wheel, for toddlers. The formula
𝟏
𝟒
𝑯(𝒕) = 𝟏𝟎 𝐬𝐢𝐧 (𝟐𝝅 (𝒕 − )) + 𝟏𝟓 models the height 𝑯 (in feet) of the bottom-most car 𝒕 minutes after the wheel
begins to rotate. Once the ride starts, it lasts 𝟒 𝐦𝐢𝐧𝐮𝐭𝐞𝐬.
a.
What is the initial height of the car?
𝟓 𝐟𝐭.
b.
How long does it take for the wheel to make one full rotation?
𝟏 𝐦𝐢𝐧𝐮𝐭𝐞
c.
What is the maximum height of the car?
𝟐𝟓 𝐟𝐭.
d.
Find the time(s) on the interval 𝟎 ≤ 𝒕 ≤ 𝟒 when the car is at its maximum height.
𝟏
𝟒
The car is at its maximum when 𝐬𝐢𝐧 (𝟐𝝅 (𝒕 − )) = 𝟏, which is at 𝒕 = 𝟎. 𝟓, 𝟏. 𝟓, 𝟐. 𝟓, and 𝟑. 𝟓 𝐦𝐢𝐧𝐮𝐭𝐞𝐬.
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Date:
Inverse Trigonometric Functions
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M4
Lesson 12
NYS COMMON CORE MATHEMATICS CURRICULUM
PRECALCULUS AND ADVANCED TOPICS
Many animal populations fluctuate periodically. Suppose that a wolf population over an 𝟖-year period is given by
8.
𝝅
𝟒
the function 𝑾(𝒕) = 𝟖𝟎𝟎 𝐬𝐢𝐧 ( 𝒕) + 𝟐𝟐𝟎𝟎, where 𝒕 represents the number of years since the initial population
counts were made.
a.
Find the time(s) on the interval 𝟎 ≤ 𝒕 ≤ 𝟖 such that the wolf population equals 𝟐𝟓𝟎𝟎.
𝒕 = 𝟎. 𝟒𝟖𝟗, 𝟑. 𝟓𝟏𝟏
The wolf population equals 𝟐𝟓𝟎𝟎 after approximately 𝟎. 𝟓 𝐲𝐞𝐚𝐫𝐬 and again after 𝟑. 𝟓 𝐲𝐞𝐚𝐫𝐬.
b.
On what time interval during the 𝟖-year period is the population below 𝟐𝟎𝟎𝟎?
𝑾(𝒕) = 𝟐𝟎𝟎𝟎 at 𝒕 = 𝟒. 𝟑𝟑𝟐 and 𝟕. 𝟔𝟕𝟖
The wolf population is below 𝟐𝟎𝟎𝟎 on the time interval (𝟒. 𝟑𝟑𝟐, 𝟕. 𝟔𝟕𝟖).
c.
Why would an animal population be an example of a periodic phenomenon?
An animal population might increase while their food source is plentiful. Then, when the population becomes
too large, there is less food and the population begins to decrease. At a certain point, there are few enough
animals that there is plenty of food for the entire population at which point the population begins to increase
again.
Closing (3 minutes)
Use the following questions to summarize the lesson and check for student understanding.

What does 𝑦 = sin−1 (𝑥) mean?


𝜋
such that sin(𝑦) = 𝑥.
2
Is cosecant the same as inverse sine?


𝜋
2
It means find the value 𝑦 on the interval − ≤ 𝑦 ≤
No. Cosecant is the reciprocal of sine not the inverse of sine.
Suzanne says that tan−1 (−√3) is
5𝜋
3
𝜋
3
. When Rosanne says that it is − , Suzanne says either answer is fine
because the two rotations lie on the same spot on the unit circle. What is wrong with Suzanne’s thinking?
MP.3

𝜋
3
tan−1 (−√3) = − and cannot equal
5𝜋
3
because
5𝜋
3
is outside of the restricted range. Because inverse
𝜋
2
𝜋
tangent is a function, there can only be one output value. That value must lie between − and .
2
Exit Ticket (5 minutes)
Lesson 12:
Date:
Inverse Trigonometric Functions
2/6/16
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Lesson 12
NYS COMMON CORE MATHEMATICS CURRICULUM
M4
PRECALCULUS AND ADVANCED TOPICS
Name
Date
Lesson 12: Inverse Trigonometric Functions
Exit Ticket
1.
State the domain and range for 𝑓(𝑥) = sin−1 (𝑥), 𝑔(𝑥) = cos −1 (𝑥), and ℎ(𝑥) = tan−1 (𝑥).
2.
Solve each trigonometric equation such that 0 ≤ 𝑥 ≤ 2𝜋. Give answers in exact form.
3.
a.
2 sin(𝑥) + √3 = 0
b.
tan2 (𝑥) − 1 = 0
Solve the trigonometric equation such that 0 ≤ 𝑥 ≤ 2𝜋. Round to three decimal places.
√5 cos(𝑥) − 2 = 0
Lesson 12:
Date:
Inverse Trigonometric Functions
2/6/16
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Lesson 12
NYS COMMON CORE MATHEMATICS CURRICULUM
M4
PRECALCULUS AND ADVANCED TOPICS
Exit Ticket Sample Solutions
1.
State the domain and range for 𝒇(𝒙) = 𝐬𝐢𝐧−𝟏 (𝒙), 𝒈(𝒙) = 𝐜𝐨𝐬 −𝟏 (𝒙), and 𝒉(𝒙) = 𝐭𝐚𝐧−𝟏 (𝒙).
For 𝒇, the domain is all real numbers 𝒙, such that −𝟏 ≤ 𝒙 ≤ 𝟏, and the range is all real numbers 𝒚, such that
−
𝝅
𝝅
≤𝒚≤ .
𝟐
𝟐
For 𝒈, the domain is all real numbers 𝒙, such that −𝟏 ≤ 𝒙 ≤ 𝟏, and the range is all real numbers 𝒚, such that
𝟎 ≤ 𝒚 ≤ 𝝅.
For 𝒉, the domain is all real numbers 𝒙, and the range is all real numbers 𝒚, such that −
2.
Solve each trigonometric equation such that 𝟎 ≤ 𝒙 ≤ 𝟐𝝅. Give answers in exact form.
a.
𝟐 𝐬𝐢𝐧(𝒙) + √𝟑 = 𝟎
𝒙=
b.
𝟒𝝅 𝟓𝝅
,
𝟑 𝟑
𝐭𝐚𝐧𝟐 (𝒙) − 𝟏 = 𝟎
𝒙=
3.
𝝅
𝝅
≤𝒚≤ .
𝟐
𝟐
𝝅 𝟑𝝅 𝟓𝝅 𝟕𝝅
,
,
,
𝟒 𝟒 𝟒 𝟒
Solve the trigonometric equation such that 𝟎 ≤ 𝒙 ≤ 𝟐𝝅. Round to three decimal places.
√𝟓 𝐜𝐨𝐬(𝒙) − 𝟐 = 𝟎
𝒙 = 𝟎. 𝟒𝟔𝟒, 𝟓. 𝟖𝟏𝟗
Problem Set Sample Solutions
1.
Solve the following equations. Approximate values of the inverse trigonometric functions to the thousandths place,
where 𝒙 refers to an angle measured in radians.
a.
𝟓 = 𝟔 𝐜𝐨𝐬(𝒙)
𝟐𝝅𝒌 ± 𝟎. 𝟓𝟖𝟔
b.
c.
𝟏
𝟐
𝝅
𝟒
− = 𝟐 𝐜𝐨𝐬 (𝒙 − ) + 𝟏
𝟐𝝅𝒌 +
𝟓𝝅
− 𝟎. 𝟕𝟐𝟑
𝟒
𝟐𝝅𝒌 −
𝟑𝝅
+ 𝟎. 𝟕𝟐𝟑
𝟒
𝟏 = 𝐜𝐨𝐬(𝟑(𝒙 − 𝟏))
𝟐𝝅𝒌
+𝟏
𝟑
Lesson 12:
Date:
Inverse Trigonometric Functions
2/6/16
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NYS COMMON CORE MATHEMATICS CURRICULUM
Lesson 12
M4
PRECALCULUS AND ADVANCED TOPICS
d.
𝟏. 𝟐 = −𝟎. 𝟓 𝐜𝐨𝐬(𝝅𝒙) + 𝟎. 𝟗
−𝟎. 𝟗𝟐𝟕 + 𝝅 + 𝟐𝝅𝒌
𝝅
𝟎. 𝟗𝟐𝟕 − 𝝅 + 𝟐𝝅𝒌
𝝅
e.
𝟕 = −𝟗 𝐜𝐨𝐬(𝒙) − 𝟒
No solutions.
f.
𝟐 = 𝟑 𝐬𝐢𝐧(𝒙)
𝟎. 𝟕𝟑𝟎 + 𝟐𝝅𝒌
𝝅 − 𝟎. 𝟕𝟑𝟎 + 𝟐𝝅𝒌
g.
−𝟏 = 𝐬𝐢𝐧 (
𝝅(𝒙−𝟏)
)−𝟏
𝟒
𝟒𝒌 + 𝟏
h.
𝝅 = 𝟑 𝐬𝐢𝐧(𝟓𝒙 + 𝟐) + 𝟐
𝟎. 𝟑𝟗𝟎 − 𝟐 + 𝟐𝝅𝒌
𝟓
𝝅 − 𝟎. 𝟑𝟗𝟎 − 𝟐 + +𝟐𝝅𝒌
𝟓
i.
𝟏
𝟗
=
𝐬𝐢𝐧(𝒙)
𝟒
𝟎. 𝟒𝟔𝟏 + 𝟐𝝅𝒌
𝝅 − 𝟎. 𝟒𝟔𝟏 + 𝟐𝝅𝒌
j.
𝐜𝐨𝐬(𝒙) = 𝐬𝐢𝐧(𝒙)
𝟏=
𝝅
𝟒
k.
𝐬𝐢𝐧(𝒙)
= 𝐭𝐚𝐧(𝒙)
𝐜𝐨𝐬(𝒙)
+ 𝝅𝒌 (or 𝟎. 𝟕𝟖𝟓 + 𝝅𝒌)
𝐬𝐢𝐧−𝟏 (𝐜𝐨𝐬(𝒙)) =
𝟐𝝅𝒌 ±
l.
𝝅
𝟑
𝝅
𝟔
𝐭𝐚𝐧(𝒙) = 𝟑
𝟏. 𝟐𝟒𝟗 + 𝝅𝒌
Lesson 12:
Date:
Inverse Trigonometric Functions
2/6/16
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Lesson 12
NYS COMMON CORE MATHEMATICS CURRICULUM
M4
PRECALCULUS AND ADVANCED TOPICS
−𝟏 = 𝟐 𝐭𝐚𝐧(𝟓𝒙 + 𝟐) − 𝟑
m.
𝝅
− 𝟐 + 𝝅𝒌
𝟒
𝟓
Alternatively,
𝟎.𝟕𝟖𝟓−𝟐+𝝅𝒌
.
𝟓
𝟓 = −𝟏. 𝟓 𝐭𝐚𝐧(−𝒙) − 𝟑
n.
𝟏. 𝟑𝟖𝟓 + 𝝅𝒌
2.
Fill out the following tables.
𝒙
−𝟏
𝐜𝐨𝐬 −𝟏 (𝒙)
𝒙
𝐬𝐢𝐧−𝟏 (𝒙)
𝐜𝐨𝐬 −𝟏 (𝒙)
−
𝝅
𝟐
𝝅
𝟎
𝟎
𝝅
𝟐
−
√𝟑
𝟐
−
𝝅
𝟑
𝟓𝝅
𝟔
𝟏
𝟐
𝝅
𝟔
𝝅
𝟑
−
√𝟐
𝟐
−
𝝅
𝟒
𝟑𝝅
𝟒
√𝟐
𝟐
𝝅
𝟒
𝝅
𝟒
𝟏
𝟐
−
𝝅
𝟔
𝟐𝝅
𝟑
√𝟑
𝟐
𝝅
𝟑
𝝅
𝟔
𝟏
𝝅
𝟐
𝟎
−
3.
𝐬𝐢𝐧−𝟏 (𝒙)
Let the velocity 𝒗 in miles per second of a particle in a particle accelerator after 𝒕 seconds be modeled by the
function 𝒗 = 𝐭𝐚𝐧 (
a.
𝝅𝒕
𝝅
− ) on an unknown domain.
𝟔𝟎𝟎𝟎 𝟐
What is the 𝒕-value of the first vertical asymptote to the right of the 𝒚-axis?
𝒕 = 𝟔𝟎𝟎𝟎
b.
If the particle accelerates to 𝟗𝟗% of the speed of light before stopping, then what is the domain?
Note: 𝒄 ≈ 𝟏𝟖𝟔𝟎𝟎𝟎. Round your solution to the ten-thousandths place.
𝟎. 𝟗𝟗 ⋅ 𝟏𝟖𝟔𝟎𝟎𝟎 = 𝟏𝟖𝟒𝟏𝟒𝟎
𝝅𝒕
𝝅
𝟏𝟖𝟒𝟏𝟒𝟎 = 𝐭𝐚𝐧 (
− )
𝟔𝟎𝟎𝟎 𝟐
𝝅𝒕
𝝅
𝐭𝐚𝐧−𝟏 (𝟏𝟖𝟒𝟏𝟒𝟎) =
−
𝟔𝟎𝟎𝟎 𝟐
𝟔𝟎𝟎𝟎
𝝅
⋅ (𝐭𝐚𝐧−𝟏 (𝟏𝟖𝟒𝟏𝟒𝟎) + ) = 𝒕
𝝅
𝟐
𝒕 ≈ 𝟓𝟗𝟗𝟗. 𝟗𝟖𝟗𝟔
So the domain is 𝟎 < 𝒕 ≤ 𝟓𝟗𝟗𝟗. 𝟗𝟖𝟗𝟔.
c.
How close does the domain get to the vertical asymptote of the function?
Very close. They are only different at the hundredths place.
Lesson 12:
Date:
Inverse Trigonometric Functions
2/6/16
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Lesson 12
NYS COMMON CORE MATHEMATICS CURRICULUM
M4
PRECALCULUS AND ADVANCED TOPICS
d.
How long does it take for the particle to reach the velocity of Earth around the sun (about
𝟏𝟖. 𝟓 𝐦𝐢𝐥𝐞𝐬 𝐩𝐞𝐫 𝐬𝐞𝐜𝐨𝐧𝐝)?
𝝅𝒕
𝝅
− )
𝟔𝟎𝟎𝟎 𝟐
𝝅𝒕
𝝅
𝐭𝐚𝐧−𝟏 (𝟏𝟖. 𝟓) =
−
𝟔𝟎𝟎𝟎 𝟐
𝟔𝟎𝟎𝟎
𝝅
⋅ (𝐭𝐚𝐧−𝟏 (𝟏𝟖. 𝟓) + ) = 𝒕
𝝅
𝟐
𝒕 ≈ 𝟓𝟖𝟗𝟔. 𝟖𝟔𝟒
𝟏𝟖. 𝟓 = 𝐭𝐚𝐧 (
It takes approximately 𝟓𝟖𝟗𝟔. 𝟖𝟔𝟒 seconds to reach the velocity of Earth around the sun.
e.
What does it imply that 𝒗 is negative up until 𝒕 = 𝟑𝟎𝟎𝟎?
The particle is traveling in the opposite direction.
Lesson 12:
Date:
Inverse Trigonometric Functions
2/6/16
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233
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