<< Chapter < Page Chapter >> Page >

On these restricted domains, we can define the inverse trigonometric functions .

  • The inverse sine function     y = sin 1 x means x = sin y . The inverse sine function is sometimes called the arcsine    function, and notated arcsin x .
    y = sin 1 x has domain [ −1 , 1 ] and range [ π 2 , π 2 ]
  • The inverse cosine function     y = cos 1 x means x = cos y . The inverse cosine function is sometimes called the arccosine    function, and notated arccos x .
    y = cos 1 x has domain [ −1 , 1 ] and range [ 0 , π ]
  • The inverse tangent function     y = tan 1 x means x = tan y . The inverse tangent function is sometimes called the arctangent    function, and notated arctan x .
    y = tan 1 x has domain ( −∞ , ) and range ( π 2 , π 2 )

The graphs of the inverse functions are shown in [link] , [link] , and [link] . Notice that the output of each of these inverse functions is a number, an angle in radian measure. We see that sin 1 x has domain [ −1 , 1 ] and range [ π 2 , π 2 ] , cos 1 x has domain [ −1 ,1 ] and range [ 0 , π ] , and tan 1 x has domain of all real numbers and range ( π 2 , π 2 ) . To find the domain    and range    of inverse trigonometric functions, switch the domain and range of the original functions. Each graph of the inverse trigonometric function is a reflection of the graph of the original function about the line y = x .

A graph of the functions of sine of x and arc sine of x. There is a dotted line y=x between the two graphs, to show inverse nature of the two functions
The sine function and inverse sine (or arcsine) function
A graph of the functions of cosine of x and arc cosine of x. There is a dotted line at y=x to show the inverse nature of the two functions.
The cosine function and inverse cosine (or arccosine) function
A graph of the functions of tangent of x and arc tangent of x. There is a dotted line at y=x to show the inverse nature of the two functions.
The tangent function and inverse tangent (or arctangent) function

Relations for inverse sine, cosine, and tangent functions

For angles in the interval [ π 2 , π 2 ] , if sin y = x , then sin 1 x = y .

For angles in the interval [ 0 , π ] , if cos y = x , then cos 1 x = y .

For angles in the interval ( π 2 , π 2 ) , if tan y = x , then tan 1 x = y .

Writing a relation for an inverse function

Given sin ( 5 π 12 ) 0.96593 , write a relation involving the inverse sine.

Use the relation for the inverse sine. If sin y = x , then sin 1 x = y .

In this problem, x = 0.96593 , and y = 5 π 12 .

sin 1 ( 0.96593 ) 5 π 12
Got questions? Get instant answers now!
Got questions? Get instant answers now!

Given cos ( 0.5 ) 0.8776, write a relation involving the inverse cosine.

arccos ( 0.8776 ) 0.5

Got questions? Get instant answers now!

Finding the exact value of expressions involving the inverse sine, cosine, and tangent functions

Now that we can identify inverse functions, we will learn to evaluate them. For most values in their domains, we must evaluate the inverse trigonometric functions by using a calculator, interpolating from a table, or using some other numerical technique. Just as we did with the original trigonometric functions, we can give exact values for the inverse functions when we are using the special angles, specifically π 6 (30°), π 4 (45°), and π 3 (60°), and their reflections into other quadrants.

Given a “special” input value, evaluate an inverse trigonometric function.

  1. Find angle x for which the original trigonometric function has an output equal to the given input for the inverse trigonometric function.
  2. If x is not in the defined range of the inverse, find another angle y that is in the defined range and has the same sine, cosine, or tangent as x , depending on which corresponds to the given inverse function.

Evaluating inverse trigonometric functions for special input values

Evaluate each of the following.

  1. sin 1 ( 1 2 )
  2. sin 1 ( 2 2 )
  3. cos 1 ( 3 2 )
  4. tan 1 ( 1 )
  1. Evaluating sin 1 ( 1 2 ) is the same as determining the angle that would have a sine value of 1 2 . In other words, what angle x would satisfy sin ( x ) = 1 2 ? There are multiple values that would satisfy this relationship, such as π 6 and 5 π 6 , but we know we need the angle in the interval [ π 2 , π 2 ] , so the answer will be sin 1 ( 1 2 ) = π 6 . Remember that the inverse is a function, so for each input, we will get exactly one output.
  2. To evaluate sin 1 ( 2 2 ) , we know that 5 π 4 and 7 π 4 both have a sine value of 2 2 , but neither is in the interval [ π 2 , π 2 ] . For that, we need the negative angle coterminal with 7 π 4 : sin 1 ( 2 2 ) = π 4 .
  3. To evaluate cos 1 ( 3 2 ) , we are looking for an angle in the interval [ 0 , π ] with a cosine value of 3 2 . The angle that satisfies this is cos 1 ( 3 2 ) = 5 π 6 .
  4. Evaluating tan 1 ( 1 ) , we are looking for an angle in the interval ( π 2 , π 2 ) with a tangent value of 1. The correct angle is tan 1 ( 1 ) = π 4 .
Got questions? Get instant answers now!
Got questions? Get instant answers now!

Questions & Answers

A golfer on a fairway is 70 m away from the green, which sits below the level of the fairway by 20 m. If the golfer hits the ball at an angle of 40° with an initial speed of 20 m/s, how close to the green does she come?
Aislinn Reply
cm
tijani
what is titration
John Reply
what is physics
Siyaka Reply
A mouse of mass 200 g falls 100 m down a vertical mine shaft and lands at the bottom with a speed of 8.0 m/s. During its fall, how much work is done on the mouse by air resistance
Jude Reply
Can you compute that for me. Ty
Jude
what is the dimension formula of energy?
David Reply
what is viscosity?
David
what is inorganic
emma Reply
what is chemistry
Youesf Reply
what is inorganic
emma
Chemistry is a branch of science that deals with the study of matter,it composition,it structure and the changes it undergoes
Adjei
please, I'm a physics student and I need help in physics
Adjanou
chemistry could also be understood like the sexual attraction/repulsion of the male and female elements. the reaction varies depending on the energy differences of each given gender. + masculine -female.
Pedro
A ball is thrown straight up.it passes a 2.0m high window 7.50 m off the ground on it path up and takes 1.30 s to go past the window.what was the ball initial velocity
Krampah Reply
2. A sled plus passenger with total mass 50 kg is pulled 20 m across the snow (0.20) at constant velocity by a force directed 25° above the horizontal. Calculate (a) the work of the applied force, (b) the work of friction, and (c) the total work.
Sahid Reply
you have been hired as an espert witness in a court case involving an automobile accident. the accident involved car A of mass 1500kg which crashed into stationary car B of mass 1100kg. the driver of car A applied his brakes 15 m before he skidded and crashed into car B. after the collision, car A s
Samuel Reply
can someone explain to me, an ignorant high school student, why the trend of the graph doesn't follow the fact that the higher frequency a sound wave is, the more power it is, hence, making me think the phons output would follow this general trend?
Joseph Reply
Nevermind i just realied that the graph is the phons output for a person with normal hearing and not just the phons output of the sound waves power, I should read the entire thing next time
Joseph
Follow up question, does anyone know where I can find a graph that accuretly depicts the actual relative "power" output of sound over its frequency instead of just humans hearing
Joseph
"Generation of electrical energy from sound energy | IEEE Conference Publication | IEEE Xplore" ***ieeexplore.ieee.org/document/7150687?reload=true
Ryan
what's motion
Maurice Reply
what are the types of wave
Maurice
answer
Magreth
progressive wave
Magreth
hello friend how are you
Muhammad Reply
fine, how about you?
Mohammed
hi
Mujahid
A string is 3.00 m long with a mass of 5.00 g. The string is held taut with a tension of 500.00 N applied to the string. A pulse is sent down the string. How long does it take the pulse to travel the 3.00 m of the string?
yasuo Reply
Who can show me the full solution in this problem?
Reofrir Reply
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply
Practice Key Terms 6

Get Jobilize Job Search Mobile App in your pocket Now!

Get it on Google Play Download on the App Store Now




Source:  OpenStax, Algebra and trigonometry. OpenStax CNX. Nov 14, 2016 Download for free at https://legacy.cnx.org/content/col11758/1.6
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Algebra and trigonometry' conversation and receive update notifications?

Ask