Chapter 12: Problem 38
Evaluating One-Sided Limits graph the function. Determine the limit (if it exists) by evaluating the corresponding one-sided limits. $$ \lim _{x \rightarrow 1} \frac{1}{x^{2}+1} $$
Short Answer
Expert verified
\(\lim _{x \rightarrow 1} \frac{1}{x^{2}+1} = 0.500\).
Step by step solution
01
One-sided limit from the left
To evaluate the one-sided limit from the left (\(x\) approaches 1 from values less than 1), we substitute \(x\) with a value slightly less than 1 into the function. For instance \(x = 0.999\). \(\lim _{x \rightarrow 1^{-}} \frac{1}{x^{2}+1} = \frac{1}{(0.999)^{2}+1} = 0.500\). We can see here the function is approaching the value \(0.500\) as \(x\) approaches 1 from the left.
02
One-sided limit from the right
To evaluate the one-sided limit from the right (\(x\) approaches 1 from values greater than 1), we substitute \(x\) with a value slightly greater than 1 into the function. For example \(x = 1.001\). \(\lim _{x \rightarrow 1^{+}} \frac{1}{x^{2}+1} = \frac{1}{(1.001)^{2}+1} = 0.500\). Here we see that the function is also approaching the value \(0.500\) as \(x\) approaches 1 from the right.
03
Evaluating the Limit
Since the one-sided limits from both the left and the right are equal at 0.500, that means the overall limit exists and is equal to 0.500. Thus, \(\lim _{x \rightarrow 1} \frac{1}{x^{2}+1} = 0.500\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Limit Evaluation
When evaluating limits, especially one-sided limits, it’s important to consider the approach from both the left and the right of a particular point. This is essential in understanding if a limit exists as you approach that point.
Here is how you tackle a one-sided limit evaluation:
Here is how you tackle a one-sided limit evaluation:
- **One-sided limits** involve analyzing the behavior of a function as it approaches a specific point from just one side (either the left or right). In the example given, this includes evaluating \( \lim_{x \to 1^{-}} \) and \( \lim_{x \to 1^{+}} \).
- Accurate **substitution** is required by choosing values very close to the point of interest from either side. For example, substituting values like \( x = 0.999 \) and \( x = 1.001 \) helps estimate the behavior of \( \frac{1}{x^2 + 1} \) as \( x \) approaches 1.
- If both one-sided limits are equal, then the general limit, \( \lim_{x \to 1} \), exists and is equal to that common value.
Graphical Analysis
Graphical analysis is another powerful method to understand limits, including one-sided limits. By visualizing the function on a graph, you can plainly see how it behaves as it approaches specific values.
Consider graphing the function \( \frac{1}{x^2+1} \):
Consider graphing the function \( \frac{1}{x^2+1} \):
- **Plotting the function** helps visualize both directions as \( x \) closes in on your point of interest, in this scenario, as \( x \) approaches 1.
- By identifying the trend lines, we can see how values converge to a specific number as we get closer to \( x = 1 \) from both sides.
- Visual indications on the graph help confirm if a function consistently nears a particular limit from different directions, in this case, matching the result found in the step-by-step evaluation.
Calculus Concepts
In calculus, understanding limits is foundational to grasping more advanced concepts like derivatives and integrals. Let’s delve into why one-sided limits are pivotal:
- **Continuity:** One-sided limits help determine whether a function is continuous at a point. For a function to be continuous at a point, the one-sided limits must be the same, which means the overall limit exists at that point.
- **Differentiability:** If functions differ in their one-sided limits, the function may not be differentiable at that point. Evaluating these limits cautions us about points of discontinuity or sharp turns.
- **Smooth Analysis:** By investigating limits deeply, calculus allows for smoother analysis of functions, providing the ability to predict behavior beyond static calculations.