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Arc and Inverse Trigonometric Functions (Arcsin, Arccos, Arctan, and Others)

Inverse trigonometric functions, commonly referred to as arc functions, are used to determine angles from given trigonometric ratios. These functions include arcsine, arccosine, arctangent, and arccotangent. They play an important role in solving trigonometric equations and are widely applied in mathematics, physics, and engineering. This article explains the concept of arc functions, their domains and ranges, and the key relationships between trigonometric functions and their inverses.

Inverse trigonometric functionsArcsin and arccosArc functions

~2 min read • Updated Feb 4, 2026

1. What Are Inverse Trigonometric Functions?


Inverse trigonometric functions are functions that return an angle when the value of a trigonometric ratio is known.


In other words, if the value of sin, cos, or tan of an angle is given, inverse trigonometric functions are used to find the angle itself.


2. The Concept of Arc (Arc Functions)


In mathematics, the term arc refers to the inverse of a trigonometric function.


For example, if we have:


sin θ = x

Then the angle can be written as:


θ = arcsin x

3. Arcsine Function (arcsin)


Arcsine returns the angle whose sine is equal to a given value.


y = arcsin x

Domain and Range of Arcsine:

  • Domain: -1 ≤ x ≤ 1
  • Range: -π/2 ≤ y ≤ π/2

4. Arccosine Function (arccos)


Arccosine determines the angle whose cosine equals a given value.


y = arccos x

Domain and Range of Arccosine:

  • Domain: -1 ≤ x ≤ 1
  • Range: 0 ≤ y ≤ π

5. Arctangent Function (arctan)


Arctangent returns the angle whose tangent is equal to a given value.


y = arctan x

Domain and Range of Arctangent:

  • Domain: all real numbers
  • Range: -π/2 < y < π/2

6. Arccotangent Function (arccot)


Arccotangent represents the angle whose cotangent has a specified value.


y = arccot x

Domain and Range of Arccotangent:

  • Domain: all real numbers
  • Range: 0 < y < π

7. Important Relationships Between Functions and Their Inverses


The following identities hold between trigonometric functions and their inverse functions:


sin(arcsin x) = x

cos(arccos x) = x

tan(arctan x) = x

8. Applications of Inverse Trigonometric Functions


Inverse trigonometric functions are widely used to solve trigonometric equations, calculate angles, and model real-world problems in physics, engineering, navigation, and computer graphics.


Conclusion


Arc functions, or inverse trigonometric functions, are essential tools for determining angles from trigonometric ratios. Understanding their domains, ranges, and key identities is crucial for solving advanced mathematical problems.


Written & researched by Dr. Shahin Siami

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