Inverse Trigonometric Functions: Formula, Table & Derivatives

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Inverse Trigonometric Functions are the inverse functions of the basic trigonometric functions.

  • The basic trigonometric functions include sine, cosine, tangent, cotangent, secant, and cosecant.
  • These functions are also known as arcus functions, anti-trigonometric functions, or cyclometer functions.
  • Inverse trigonometry is applied in various fields such as physics, engineering, geometry, navigation, geometry, aviation, marine biology, etc.
  • Inverse Trigonometry is useful for obtaining angles of a triangle from any trigonometric function

Key Terms: Inverse Trigonometric Functions, Functions, Perpendicular,cotangent, secant, Tangent, trigonometric, Traingle, sine, cosine, tangent, cotangent, secant, cosecant


Definition of Inverse Trigonometric Functions

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Inverse trigonometric Functions are known as the anti-trigonometric functions as they are the inverse of trigonometric functions.

  • They are also known as the ''Arc Functions''.
  • Inverse Trigonometric Functions perform opposite functions of the trigonometric Functions.
  • These functions are useful for finding angles when any two sides of a right-angled triangle are given.
  • The inverse trigonometric functions are written with the prefix 'arc'.

Also Read:


Formulas Of Inverse Trigonometric Functions

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Inverse Trigonometric Formulas are necessary to solve the questions.

Some basic trigonometric formulas are-:

  • sin-1(-x) = -sin-1(x), x ∈ [-1, 1]
  • cos-1(-x) = π -cos-1(x), x ∈ [-1, 1]
  • tan-1(-x) = -tan-1(x), x ∈ R
  • cot-1(-x) = π – cot-1(x), x ∈ R
  • sec-1(-x) = π -sec-1(x), |x| ≥ 1
  • cosec-1(-x) = -cosec-1(x), |x| ≥ 1
  • sin-1x + cos-1x = π/2, x ∈ [-1,1]
  • tan-1x+ cot-1x = π/2, x ∈ R
  • sec-1x + cosec-1x = π/2, x ∈ R - [-1,1]
  • sin-1x = cosec-11/x, x ∈ R - (-1,1)
  • cos-1x = sec-11/x, x ∈ R - (-1,1)
  • tan-1x = cot-11/x, x > 0
  • tan-1x = - π + cot-1 x, x < 0
  • sin-1x + sin-1y = sin-1(x.(1 - y2) + y√(1 - x2))
  • sin-1x - sin-1y = sin-1(x.(1 - y2) - y√(1 - x2))
  • cos-1x + cos-1y = cos-1(xy - (1 - x2).√(1 - y2))
  • cos-1x - cos-1y = cos-1(xy + (1 - x2).√(1 - y2))
  • tan-1x + tan-1y = tan-1(x + y)/(1 - xy), if xy < 1
  • tan-1x + tan-1y = tan-1(x - y)/(1 + xy), if xy > - 1

Graphs Of Inverse Trigonometric Functions

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The graphs of inverse trigonometric functions are given below

sin-1x Graph

sin-1x is the inverse of the sine function. It is denoted by the graph as shown below-:

sin-1x Graph
sin-1x Graph
  • Domain = -1 ≤ x ≤ 1
  • Range = -π/2 ≤ y ≤ π/2

cos-1(x) Graph

cos-1(x) is the inverse of the cosine function. It is denoted by the graph as shown below-:

cos-1(x) Graph
cos-1(x) Graph
  • Domain = -1≤ x ≤1
  • Range = 0 ≤ y ≤ π

tan-1(x) Graph

 tan-1(x) is the inverse of the tangent function. It is denoted by the graph as shown below-:

tan-1(x) Graph
tan-1(x) Graph
  • Domain = -∞ < x < ∞
  • Range =-π/2 < y < π/2

cosec-1(x) Graph

cosec-1(x) is the inverse of the Cosecant function. It is denoted by the graph as shown below-:

cosec-1(x) Graph
cosec-1(x) Graph
  • Domain = -∞ ≤ x ≤ -1 or 1 ≤ x ≤ ∞
  • Range = -π/2 ≤ y ≤ π/2, y ≠ 0

sec-1(x) Graph

sec-1(x) is the inverse of the Secant function. It is denoted by the graph as shown below-:

sec-1(x) Graph
sec-1(x) Graph
  • Domain = -∞ ≤ x ≤ -1 or 1 ≤ x ≤ ∞
  • Range 0 ≤ y ≤ π, y ≠ π/2

cot-1(x) Graph

cot-1(x) is the inverse of the Cotangent function. It is denoted by the following graph-:

cot-1(x) Graph
cot-1(x) Graph
  • Domain = -∞ < x < ∞
  • Range = 0 < y < π

Domain and Range Of Inverse Trigonometric Functions

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The graphs help in comprehending and comparing different functions.

  • The domain of a function is shown along the x-axis of a graph, while the range of a function is denoted by the y-axis of the graph.
  • Domain and range give us the principle value of the inverse trigonometric function.

The domain and range of different functions are as follows-:

Function Domain Range
y = sin-1(x) −1 ≤ x ≤ 1 − π/2 ≤ y ≤ π/2
y=cos-1(x) −1 ≤ x ≤ 1 0 ≤ y ≤ π
y=tan-1(x) All real numbers − π/2 < y < π/2
y=cosec-1(x) x ≤ −1 or 1 ≤ x −π/2≤y<0 or 0
y = sec-1(x) x ≤ −1 or 1 ≤ x 0≤y<π/2 or π/2
y=cot-1(x) All real numbers 0 < y < π

Derivative Of Inverse Trigonometric Function

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Inverse Trigonometric Functions are integral in Calculus.

  • The derivatives of inverse trigonometric functions are used to solve many questions.
  • The derivatives of these functions are first-order derivatives.

The Derivative of the functions are as follows-:

Inverse Trigonometric Function dy/dx
y = sin-1(x) 1/√(1-x2)
y = cos-1(x) -1/√(1-x2)
y = tan-1(x) 1/(1+x2)
y = cot-1(x) -1/(1+x2)
y = sec-1(x) 1/[|x|√(x2-1)]
y = cosec-1(x) -1/[|x|√(x2-1)]

Important Topics for JEE Main 

As per JEE Main 2024 Session 1, important topics included in the chapter Inverse Trigonometric Functions are as follows:

  • Formulas Of Inverse Trigonometric Functions
  • Domain and Range of Inverse Trigonometric Functions

Some memory based important questions asked in JEE Main 2024 Session 1 include:

  1. Considering the principal values of inverse trigonometric functions, find the positive real values of x satisfying tan-1(x) + tan-1(2x) = π/4.


Things to Remember

  • Inverse Trigonometric Functions are the inverse of the basic trigonometric functions like sin x, cosx, tan x, cosec x, sec x, and cot x.
  • Inverse Trigonometry is used to find the angle of a right-angled triangle when two sides are given.
  • Inverse Trigonometric functions are also known as arcus functions, anti-trigonometric functions, or cyclometer functions.
  • The domain of a function is represented along the x-axis, while the Range of a function is represented along the y-axis.
  • Derivatives of the Inverse Trigonometric Functions are also an important part of calculus.
  • They are used in solving numerous problems.

Previous Year Questions

  1. If tan−1xtan−1⁡x + tan−1ytan−1⁡y = 2π32π3 , then cot−1xcot−1⁡x + cot−1ycot−1⁡y is equal t
  2. If sin−1x+sin−1y=π2 , then cos−1x+cos−1y is equal to
  3. cos−1(−12)−2sin−1(12)+3cos−1(−1√2)−4tan−1(−1) equals
  4. The period of sin4x+cos4x is
  5. If 2tan−1(cosx)=tan−1(2cosecx) then sinx+cosx is equal to
  6. The period of tan3θ is
  7. ∫ex(1+sinx)1+cosxdx=….[COMEDK UGET 2011]
  8. If tan(x+y)=33 and x=tan−13, then y is…..[COMEDK UGET 2015]
  9. cot−1(21)+cot−1(13)+cot−1(−8)=…...[COMEDK UGET 2015]
  10. tan(cos−1(15√2)−sin−1(4√17)) is….….​.[COMEDK UGET 2015]
  11. If 12≤x≤1,12≤x≤1, then cos−1x+cos−1(x2+√3−3x22)=...[COMEDK UGET 2010]
  12. If cos−1x+cos−1y+cos−1z=3π, then xy+yz+zx is...[COMEDK UGET 2011]
  13. Define f (x) = min{x^2 + 1, x + 1] for.xe∈R. Then 1∫−1f(x)dx is...[COMEDK UGET 2005]
  14. The value of the integral π/4∫01+sin2cos3xdx is​….[COMEDK UGET 2005]
  15. tan−1(1x+y)+tan−1(yx2+xy+1)=​…...[COMEDK UGET 2011]
  16. tan[12sin−1(2x1+x2)+12cos−1(1−x21+x2)]=….[COMEDK UGET 2007]
  17. The value of tan−1√2+√3−√2−√3√2+√3+√2−√3….[COMEDK UGET 2008]
  18. The value of cot−1{√1−sinx+√1+sinx√1−sinx−√1+sinx}(0<x<π2) is​
  19. In a ΔABC, if A=tan−12 and B=tan−13 , then C=​
  20. sin−1(1√e)>tan−1(1√π)sin−1(1e)>tan−1(1π) sin−1x>tan−1ysin−1x>tan−1y for x>y,∀x,y∈(0,1)​

Sample Questions

Ques. Prove that tan-1 2/11 + tan-1 7/24 = tan-1 1/2. (4 marks)

Ans. By using the formula tan-1 x + tan-1 y = tan-1 (x + y) / (1 - xy)

We get, LHS = tan-1 2/11 + tan-1 7/24

= tan-1 [(2/11 + 7/24) / (1 - (2/11). (7/24)]

= tan-1 [((48 + 77) / 264) / ((264 - 14) / 264)]

On simplifying the terms,

= tan-1 (125 / 250)

= tan-1(1 / 2)

= RHS

Ques. Find the value of x for sin(x) = 2. (2 marks)

Ans. Given, sin (x) = 2

⇒ x =sin-1(2), which is not possible.

Hence, there is no value of x for which sin x = 2, so the domain of sin-1x is -1 to 1 for the values of x.

Ques. Find the value of tan (sin-1 3/5 + cot-1 3/2). (5 marks)

Ans. Here the basic trigonometric function of sin x = y can be changed to x = sin-1 y

Let sin-1 3/5 = x

⇒ sin x = 3/5

Then, cos x = √ 1 - sin2 x

= 4/5

⇒ sec x = 5/4

Therefore, tan x = √ sec2 x - 1

= √ ( 25/16) - 1

= 3 / 4

x = tan-1 3/4

sin-1 3 / 5 = tan-1 3 / 4 ....(1)

Now, cot-1 3 / 2 = tan-1 2 / 3 ....(2)

By using equation (1) and (2)

tan (sin-1 3/5 + cot-1 2/3) = tan (tan-1 3/4 + tan-1 2/3)

= tan [tan-1 (3/4 + 2/3) / (1 - (3/4).(2/3)]

= tan (tan-1 17 / 6)

= 17 / 6

Ques. Find the values of tan-1 √3 - cot-1 (- √3). (4 marks)

Ans. Here the basic trigonometric function of sinx = y, can be changed to x = sin-1 y

Let tan-1 √3 = x

So, tan x = √3

= tan π / 3

where π / 3 ∈ (- π/2, π/2)

So, tan-1 √3 = π/3

Let us assume cot-1 (- √3) = y

Hence, cot y = (- √3)

= - cot (π / 6)

= cot (π - π / 6)

= cot (5π / 6)

Since, Range of principal value of cot-1 x = (0, π)

Therefore, cot-1(- √3) = (5π / 6)

Then, tan-1 √3 - cot-1 (- √3)

= π / 3 - 5π / 6

= - π / 2

Ques. Prove that 3 sin-1 x = sin-1 (3x - 4x3), x ∈ [- 1/2, 1/2]. (4 marks)

Ans. The basic trigonometric function of Sin θ = y can be changed to θ = sin-1 y

Let x =sin θ 

Hence, sin-1 (x) = θ

Now,

RHS = sin-1 (3x - 4x3)

Using the trigonometric function

sin 3 θ = 3 sin θ - 4 sin3 θ

= sin-1 (3sin θ - 4sin3 θ)

= sin-1 (sin 3θ)

= 3 θ

= 3 sin-1 x

= LHS

Ques. Find sin (cos-1 3/5). (2 marks)

Ans. Let cos-1 3/5 = x 

⇒ cos x = 3/5

We have, sin x = √(1 – cos2 x)

⇒ sin x = √(1 – 9/15) = 4/5

⇒ sin x = sin (cos-1 3/5) = 4/5

Ques. Solve: 2 tan-1 (cos x) = tan-1 (2cosec x). (4 marks)

Ans. Basic trigonometric function of sin θ = y can be changed to θ = sin-1 y

It is given that 2 tan-1 (cos x)

= tan-1 (2 cosec x).

Since, 2 tan-1 (x) = tan-1 2x/(1 + x2)

Hence,

⇒ tan-1 [(2 cos x)/(1- cos2 x)]

= tan-1 (2 cosec x)

⇒ (2 cos x) / (sin2 x)

= 2/sin x

⇒ cos x = sin x

⇒ tanx = 1

⇒ tan x

= tan π/4

Therefore,

x = nπ + π/4, where n ∈ Z

Ques. Find the value of sin-1(sin π/6). (1 mark)

Ans. From identity sin-1(sin x) = x, we have

sin-1(sin π/6) = π/6

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1.
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                        CBSE CLASS XII Previous Year Papers

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