Chapter 4: Problem 5
Explain how to convert a limit of the form 0 . \(\infty\) to a limit of the form \(0 / 0\) or \(\infty / \infty\).
Short Answer
Expert verified
Answer: The given limit is in the form 0 . ∞.
Step by step solution
01
Identify the limit
First, let's identify the limit in the form \(0 . \infty\). For this example, we will consider the limit:
$$
\lim_{x \to 0} (x \cdot f(x))
$$
Here, \(\lim_{x \to 0} x = 0\) and we assume that \(\lim_{x \to 0} f(x) = \infty\).
02
Introduce a new function
Let's introduce a new function, \(g(x)\) such that \(g(x) = \frac{1}{f(x)}\). Then, \(\lim_{x \to 0} g(x) = \frac{1}{\infty} = 0\). The given limit can now be written as:
$$
\lim_{x \to 0} \left(x \cdot \frac{1}{g(x)}\right)
$$
03
Rewrite the given limit
Now, let's rewrite the given limit in terms of a fraction by multiplying the numerator and denominator by \(g(x)\). This gives us:
$$
\lim_{x \to 0} \left(\frac{x \cdot 1}{g(x)} \cdot \frac{g(x)}{1}\right)
$$
This simplifies to:
$$
\lim_{x \to 0} \frac{x \cdot g(x)}{1} = \lim_{x \to 0} \frac{x}{f(x)}
$$
04
Check the new form
We can now see the limit is in the desired form. As \(x \to 0\), the new function becomes:
$$
\lim_{x \to 0} \frac{x}{f(x)} = \lim_{x \to 0} \frac{0}{\infty} = 0 \over \infty
$$
Therefore, we have successfully converted the given limit of the form \(0 . \infty\) into a limit of the form \(0 / \infty\). Remember that this is just an example, and the specific steps may vary depending on the given limit.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Indeterminate Forms
In calculus, the term **indeterminate form** refers to specific types of limits where direct substitution leads to forms such as \(0/0\) or \(\infty/\infty\), among others. Each of these forms indicates uncertainty, as standard calculation methods cannot provide a clear answer. With an indeterminate form, further analysis is required to determine the limit's true value.
When dealing with limits, such forms arise when the behavior of the function around a particular point is not straightforward. For example, a limit like \(0 \cdot \infty\) is indeterminate because multiplying zero by infinity does not have a definite outcome.
When dealing with limits, such forms arise when the behavior of the function around a particular point is not straightforward. For example, a limit like \(0 \cdot \infty\) is indeterminate because multiplying zero by infinity does not have a definite outcome.
- In the form \(0/0\), both the numerator and denominator approach zero, leading to uncertainty.
- The form \(\infty/\infty\) implies both the numerator and denominator are growing without bound, creating similar ambiguity.
Calculus Techniques
There are several **calculus techniques** used to resolve limits that present indeterminate forms. One essential technique is L'Hopital's Rule, which is specifically designed for evaluating limits that result in indeterminate forms of the type \(0/0\) or \(\infty/\infty\). By differentiating the numerator and the denominator, L'Hopital’s Rule helps simplify the limit calculation.
- Another common technique is algebraic manipulation, where you rewrite the function in a form that's easier to evaluate.
- Factoring, multiplying by a conjugate, and trigonometric identities are also useful for converting indeterminate forms into determinate ones.
Mathematical Limits
**Mathematical Limits** are foundational in calculus, representing how a function behaves as its input approaches a certain value. Calculating limits often involves simplifying the function's expression to find its value as the independent variable nears a particular point.
- Limits are essential for understanding the behavior of functions at points of discontinuity or where they trend towards infinity.
- They form the basis for defining derivatives and integrals, the core concepts of calculus.