The Problem of Multiple Antiderivatives

Oct 13, 2025 by wbrum.org 25 views

Introduction

In the realm of calculus, particularly in the context of integration, the concept of antiderivatives plays a crucial role. An antiderivative of a function $f(x)$ is a function $F(x)$ such that the derivative of $F(x)$ is equal to $f(x)$ . However, when it comes to manual integration or the use of Computer Algebra Systems (CAS), the results can vary significantly. In this article, we will delve into the domain of antiderivatives and explore how CAS can influence the outcome of integration.

The Problem of Multiple Antiderivatives

When integrating a function $f(x)$ , there can be multiple antiderivatives, each differing by a constant. This is due to the fact that the derivative of a constant is zero, and therefore, adding a constant to an antiderivative does not change its derivative. For instance, consider the function $f(x) = x^2$ . One antiderivative of $f(x)$ is $F(x) = \frac{x^3}{3}$ . However, another antiderivative is $G(x) = \frac{x^3}{3} + C$ , where $C$ is an arbitrary constant.

Computer Algebra Systems and Integration

Computer Algebra Systems (CAS) are powerful tools that can perform various mathematical operations, including integration. CAS can be used to find antiderivatives of functions, but the results can be influenced by the choices made during the integration process. For example, consider the function $f(x) = \frac{1}{x}$ . Using a CAS, we can find two antiderivatives: $F(x) = \ln|x|$ and $G(x) = \ln|x| + C$ . However, if we use a different CAS or make different choices during the integration process, we may obtain different antiderivatives.

The Role of CAS in Determining the Domain of Antiderivatives

The domain of an antiderivative is the set of all possible values of $x$ for which the antiderivative is defined. When using a CAS to find an antiderivative, the domain of the antiderivative is determined by the choices made during the integration process. For instance, consider the function $f(x) = \frac{1}{x^2 - 4}$ . Using a CAS, we can find an antiderivative: $F(x) = \frac{1}{2} \arctan\left(\frac{x}{2}\right)$ . However, if we use a different CAS or make different choices during the integration process, we may obtain a different antiderivative with a different domain.

Examples of CAS Influencing the Domain of Antiderivatives

Example 1: Integration of $\frac{1}{x^2 - 4}$

Using a CAS, we can find two antiderivatives of $\frac{1}{x^2 - 4}$ :

$F(x) = \frac{1}{2} \arctan\left(\frac{x}{2}\right)$
$G(x) = \frac{1}{2} \arctan\left(\frac{x}{2}\right) + C$

The domain of $F(x)$ is $(-\infty, -2) \cup (-2, 2) \cup (2, \infty)$ , while the domain of $G(x)$ is also $(-\infty, -2) \cup (-2, 2) \cup (2, \infty)$ .

Example 2: Integration of $\frac{1}{x^2 + 1}$

Using a CAS, we can find two antiderivatives of $\frac{1}{x^2 + 1}$ :

$F(x) = \arctan(x)$
$G(x) = \arctan(x) + C$

The domain of $F(x)$ is $(-\infty, \infty)$ , while the domain of $G(x)$ is also $(-\infty, \infty)$ .

Example 3: Integration of $\frac{1}{x^2 - 4x + 3}$

Using a CAS, we can find two antiderivatives of $\frac{1}{x^2 - 4x + 3}$ :

$F(x) = \frac{1}{2} \ln\left|\frac{x-1}{x-3}\right|$
$G(x) = \frac{1}{2} \ln\left|\frac{x-1}{x-3}\right| + C$

The domain of $F(x)$ is $(-\infty, 1) \cup (1, 3) \cup (3, \infty)$ , while the domain of $G(x)$ is also $(-\infty, 1) \cup (1, 3) \cup (3, \infty)$ .

Conclusion

In conclusion, the domain of antiderivatives can be influenced by the choices made during manual integration or the use of Computer Algebra Systems. CAS can provide different antiderivatives, each with its own domain, depending on the choices made during the integration process. Therefore, it is essential to carefully consider the domain of an antiderivative when using a CAS to find an antiderivative.

References

[1] "Calculus" by Michael Spivak
[2] "Computer Algebra Systems" by David A. Cox
[3] "Integration" by Wolfram MathWorld

Introduction

In our previous article, we explored the domain of antiderivatives and how Computer Algebra Systems (CAS) can influence the outcome of integration. In this article, we will answer some frequently asked questions related to the domain of antiderivatives and CAS.

Q: What is the difference between an antiderivative and a derivative?

A: An antiderivative of a function $f(x)$ is a function $F(x)$ such that the derivative of $F(x)$ is equal to $f(x)$ . On the other hand, a derivative of a function $F(x)$ is a function $f(x)$ such that the antiderivative of $f(x)$ is equal to $F(x)$ .

Q: Why do CAS provide different antiderivatives?

A: CAS provide different antiderivatives because they use different algorithms and techniques to perform integration. Additionally, CAS may make different choices during the integration process, such as choosing a different antiderivative or adding a constant to the antiderivative.

Q: How can I determine the domain of an antiderivative?

A: To determine the domain of an antiderivative, you need to consider the restrictions on the function that is being integrated. For example, if the function has a denominator that is equal to zero, then the domain of the antiderivative will be restricted to exclude the values that make the denominator equal to zero.

Q: Can I use CAS to find the domain of an antiderivative?

A: Yes, you can use CAS to find the domain of an antiderivative. However, you need to be careful when using CAS to find the domain of an antiderivative, as CAS may not always provide the correct domain.

Q: What are some common mistakes to avoid when using CAS to find antiderivatives?

A: Some common mistakes to avoid when using CAS to find antiderivatives include:

Not checking the domain of the antiderivative
Not considering the restrictions on the function that is being integrated
Not adding a constant to the antiderivative
Not using the correct algorithm or technique for integration

Q: How can I verify the correctness of an antiderivative found by CAS?

A: To verify the correctness of an antiderivative found by CAS, you can use the following steps:

Check the domain of the antiderivative
Check the restrictions on the function that is being integrated
Check that the antiderivative satisfies the definition of an antiderivative
Check that the antiderivative is consistent with the given function

Q: Can I use CAS to find the antiderivative of a function that is not defined at a point?

A: Yes, you can use CAS to find the antiderivative of a function that is not defined at a point. However, you need to be careful when using CAS to find the antiderivative of a function that is not defined at a point, as CAS may not always provide the correct antiderivative.

Q: What are some real-world applications of antiderivatives?

A: Some real-world applications of antiderivatives include:

Physics: Antiderivatives are used to find the position, velocity, and acceleration of an object.
Engineering: Antiderivatives are used to find the area under curves and the volume of solids.
Economics: Antiderivatives are used to find the total cost of a function and the total revenue of a function.

Conclusion

References

[1] "Calculus" by Michael Spivak
[2] "Computer Algebra Systems" by David A. Cox
[3] "Integration" by Wolfram MathWorld