How Does the Limit of Logarithms Compare Two Functions Asymptotically?

In summary, the conversation discusses the use of limits to compare the asymptotic behavior of two functions, specifically the use of logarithms to determine if one function is greater or smaller than the other. The participants also mention the benefits of using logarithms as transformations in analyzing fast-growing functions.
  • #1
OhMyMarkov
83
0
Hello everyone!

I'm considering the problem of comparing the asymptotic behavior of two functions $f(x)$ and $g(x)$.

We can say that if $\lim _{x\rightarrow \infty} f(x) / g(x) = \infty$ then f is asymptotically greater than g. Similarly, if this limit is 0, then f is asymptotically less than g.

Now, how about if use $\lim _{x\rightarrow \infty} \log (f(x) / g(x))$, if the limit is $\infty$, then f is greater, and if the limity is $-\infty$, f is smaller, right?

Can we conclude from $\lim _{x\rightarrow \infty} \log f(x) / \log g(x)$ something about the respective behavior of f and g? It sure does help to look at logs of fast-growing functions...
 
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  • #2
Re: Limit of Ration of Two Functions

The logarithm is monotonic increasing and changes no relationship. This is why logarithms (and square roots) are popular transformations.
 

FAQ: How Does the Limit of Logarithms Compare Two Functions Asymptotically?

What is the definition of "Limit of Ratio of Two Functions?"

The limit of the ratio of two functions is the value that a function approaches as its input approaches a certain value. It is the value that the ratio of the two functions converges to as the input becomes infinitely small or large.

How is the limit of the ratio of two functions calculated?

The limit of the ratio of two functions can be calculated using the quotient rule, which states that the limit of the ratio of two functions is equal to the ratio of the limits of the two functions. This means that the limit of the ratio of two functions can be found by taking the limit of the numerator and the limit of the denominator separately.

What is the significance of the limit of the ratio of two functions in mathematics?

The limit of the ratio of two functions is an important concept in calculus and is used to determine the behavior of functions as they approach a certain value. It is also used to define the derivative of a function and plays a crucial role in solving problems related to rates of change.

Can the limit of the ratio of two functions be undefined?

Yes, the limit of the ratio of two functions can be undefined if the denominator approaches zero and the numerator does not. This is known as an "indeterminate form" and further analysis is needed to determine the limit in such cases.

How is the limit of the ratio of two functions used in real-world applications?

The limit of the ratio of two functions is used in real-world applications to model and predict the behavior of a system. For example, it can be used to calculate the speed of an object at a specific point in time, or to determine the maximum efficiency of a machine. It is also used in economics and finance to analyze growth and change in various industries.

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