Finding the limit for exponential function using Taylor Expansions

In summary, the conversation is about determining a limit and proving it using the formal definition. The student is struggling with using Taylor expansions and asks for guidance, while another person suggests using L'Hospital's rule instead.
  • #1
georgetown13
7
0

Homework Statement


Determine the limit and then prove your claim.

limx[tex]\rightarrow[/tex][tex]\infty[/tex] (1+[tex]\frac{1}{x^2} }[/tex]) x

Homework Equations



I know that the formal definition that I need to use to prove the limit is:

{limx[tex]\rightarrow[/tex][tex]\infty[/tex] (1+[tex]\frac{1}{x^2}[/tex])x=1}={[tex]\forall[/tex] [tex]\epsilon[/tex]>0, [tex]\exists[/tex] N > 0, [tex]\ni[/tex] x>N [tex]\Rightarrow[/tex] |f(x)-1|< [tex]\epsilon[/tex]}

The Attempt at a Solution



We have to use Taylor Expansions to find the Taylor polynomial of f(x) and bound the errors to solve for [tex]\delta[/tex], given [tex]\epsilon[/tex] >0.
The "x" exponent, however, is throwing me off. Could someone help guide me through the Taylor expansion of f(x)? I'd greatly appreciate it!
 
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  • #2
georgetown13 said:

Homework Statement


Determine the limit and then prove your claim.

limx[tex]\rightarrow[/tex][tex]\infty[/tex] (1+[tex]\frac{1}{x^2} }[/tex]) x


Homework Equations



I know that the formal definition that I need to use to prove the limit is:

{limx[tex]\rightarrow[/tex][tex]\infty[/tex] (1+[tex]\frac{1}{x^2}[/tex])x=1}={[tex]\forall[/tex] [tex]\epsilon[/tex]>0, [tex]\exists[/tex] N > 0, [tex]\ni[/tex] x>N [tex]\Rightarrow[/tex] |f(x)-1|< [tex]\epsilon[/tex]}

The Attempt at a Solution



We have to use Taylor Expansions to find the Taylor polynomial of f(x) and bound the errors to solve for [tex]\delta[/tex], given [tex]\epsilon[/tex] >0.
The "x" exponent, however, is throwing me off. Could someone help guide me through the Taylor expansion of f(x)? I'd greatly appreciate it!

Not offering to try the Taylor thing here; are you required to do it that way? Otherwise, I would let

[tex]y = \left( 1 + \frac 1 {x^2}\right)^x[/tex]

and work with [itex]\ln(y)[/itex] using L'Hospital's rule.
 

Related to Finding the limit for exponential function using Taylor Expansions

1. What is a Taylor Expansion?

A Taylor Expansion is a mathematical method used to approximate a function using a series of polynomial terms. It is used to find the value of a function at a certain point, by considering the values of the function and its derivatives at that point.

2. How do you use a Taylor Expansion to find the limit of an exponential function?

To find the limit of an exponential function using a Taylor Expansion, we first need to express the function as a power series. This can be done by using the Maclaurin series, which is a special case of the Taylor series. Then, we can evaluate the limit by plugging in the value we want to find the limit at into the power series.

3. Why is it important to use Taylor Expansions when finding limits?

Taylor Expansions allow us to approximate the value of a function at a certain point, without having to evaluate the function at that point directly. This can be useful when the function is complex or when the point is outside of the function's domain. Additionally, Taylor Expansions can provide a more accurate approximation of the limit compared to other methods.

4. Are there any limitations to using Taylor Expansions to find limits?

Yes, there are some limitations to using Taylor Expansions. First, the function must be differentiable at the point where the limit is being evaluated. Additionally, the series may not converge for some functions, making it impossible to use Taylor Expansions to find the limit. Lastly, using a higher order Taylor Expansion may provide a more accurate approximation, but it requires more computational effort.

5. Can Taylor Expansions be used to find the limits of other types of functions?

Yes, Taylor Expansions can be used to find the limits of a wide range of functions, including trigonometric, logarithmic, and hyperbolic functions. However, the process may be more complex for these types of functions and may require more terms in the power series to obtain an accurate approximation.

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