1.13 Removing Discontinuities

5 min read•january 23, 2023

Anusha Tekumulla

ethan_bilderbeek

AP Calculus AB/BC ♾️

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This topic focuses on how we can remove discontinuities from a function. If the limit of a function exists at a discontinuity in its graph, then it is possible to remove the discontinuity at that point so it equals the lim x -> a [f(x)].

We use two methods to remove discontinuities in AP Calculus: factoring and rationalization.

How to Remove Discontinuities

Removing discontinuities from a function is an important step in understanding the behavior of a function and making it usable for further analysis. A discontinuity in a function is a point where the function is not defined or is not continuous, and it can occur in different forms such as a hole, a jump, or an asymptote.

Here is a guide on how to remove discontinuities from a function:

Identify the type of discontinuity: There are different types of discontinuities, such as a removable discontinuity, a jump discontinuity, and an essential discontinuity. Identifying the type of discontinuity is the first step in removing it.
Removable Discontinuity: A removable discontinuity is a discontinuity that occurs when the function is not defined at a single point, but it can be made continuous by filling in that point with the appropriate value. To remove a removable discontinuity, you can either factor the numerator and cancel the common factors with the denominator, or you can use algebraic manipulation to make the function continuous.
Jump Discontinuity: A jump discontinuity is a discontinuity that occurs when the function has different values on either side of a point. To remove a jump discontinuity, you can either make the function piecewise, or you can use algebraic manipulation to make the function continuous.
Essential Discontinuity: An essential discontinuity is a discontinuity that cannot be removed by any algebraic manipulation. Essential discontinuities occur when the function has a hole, a vertical asymptote, or a horizontal asymptote at a particular point. To remove an essential discontinuity, you can either use different methods to represent the function, such as using piecewise functions, or you can use limits to understand the behavior of the function near the discontinuity. Essential discontinuities occur when the function has a hole, a vertical asymptote, or a horizontal asymptote at a particular point. To remove an essential discontinuity, you can either use different methods to represent the function, such as using piecewise functions, or you can use limits to understand the behavior of the function near the discontinuity.

Another way to deal with discontinuities is to use the concept of one-sided limits. A one-sided limit is the limit of a function as x approaches a particular value from one direction only, either from the left or from the right. In the case of essential discontinuities, one-sided limits may exist even though the two-sided limit does not. This means that the function approaches different values as x approaches the point of discontinuity from different directions.

Additionally, when dealing with a function that has an essential discontinuity at a certain point, you can use different representations of the function to understand its behavior near the discontinuity. For example, you could use a graph of the function, or you could use a table of values to see how the function behaves near the discontinuity.

It's also important to note that when you are working with real-world problems, discontinuities are not always obvious, and it may take some effort to identify them. In some cases, you may not be able to remove the discontinuity completely, but you can still use the methods described above to better understand the behavior of the function near the discontinuity.

It's also worth mentioning that in the context of Calculus, discontinuities are not always bad thing, it can have some interesting properties. For example, the differentiability of a function and its continuity are not always related, a function can be differentiable at a point but not be continuous there, this is called a point of infinite discontinuity.

In summary, removing discontinuities from a function is an important step in understanding its behavior and making it usable for further analysis. Different types of discontinuities require different methods to remove them, and it's important to use the appropriate method for each case. Additionally, it's important to understand the concept of one-sided limits and use different representations of the function to understand its behavior near the discontinuity.

Examples

Example 1: Remove the removable discontinuity from the function f(x) = (x^2 - 4)/(x - 2) Solution: The removable discontinuity in this function occurs at x = 2, because the denominator is equal to zero at that point. To remove the discontinuity, we can factor the numerator and cancel the common factor of (x-2) with the denominator. The function becomes f(x) = x + 2, which is now continuous at x = 2.

Example 2: Remove the jump discontinuity from the function g(x) = { x if x < 2, x^2 if x >= 2} Solution: The jump discontinuity in this function occurs at x = 2, because the function has different values on either side of that point. To remove the discontinuity, we can make the function piecewise, by defining a new function h(x) = x^2 for x < 2 and h(x) = x^2 for x >= 2 This new function is now continuous at x = 2.

Example 3: Remove the essential discontinuity from the function k(x) = 1/x Solution: The essential discontinuity in this function occurs at x = 0, because the function has a hole at that point. To remove the discontinuity, we can use limits to understand the behavior of the function near x = 0. The limit as x approaches 0 from the left is negative infinity and the limit as x approaches 0 from the right is positive infinity. This means that the function does not have a well-defined value at x = 0, and it is not possible to remove the discontinuity by any algebraic manipulation.

In conclusion, removing discontinuities from a function is an important step in understanding the behavior of a function and making it usable for further analysis. It's important to identify the type of discontinuity, and use the appropriate method to remove it. Removable discontinuities can be removed by algebraic manipulation, jump discontinuities can be removed by making the function piecewise, and essential discontinuities can be understood by using limits. Continuity is a fundamental concept in calculus and understanding discontinuities is crucial to being able to work with different functions.

Browse Study Guides By Unit

👑Unit 1 – Limits & Continuity

1.0Unit 1 Overview: Limits and Continuity

1.1Introducing Calculus: Can Change Occur at An Instant?

1.2Defining Limits and Using Limit Notation

1.3Estimating Limit Values from Graphs

1.4Estimating Limit Values from Tables

1.5Determining Limits Using Algebraic Properties of Limits

1.6Determining Limits Using Algebraic Manipulation

1.7Selecting Procedures for Determining Limits

1.8Determining Limits Using the Squeeze Theorem

1.10Exploring Types of Discontinuities