Finding the limit for exponential function using Taylor Expansions

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SUMMARY

The discussion focuses on determining the limit of the function limx→∞ (1 + 1/x2)x using Taylor expansions. The formal definition for proving the limit is established as limx→∞ (1 + 1/x2)x = 1, with the condition that for every ε > 0, there exists an N > 0 such that for all x > N, |f(x) - 1| < ε. Participants suggest using Taylor expansions to find the Taylor polynomial of f(x) and recommend an alternative approach using L'Hospital's rule by taking the natural logarithm of y = (1 + 1/x2)x.

PREREQUISITES
  • Understanding of limits and the formal ε-N definition of limits.
  • Familiarity with Taylor expansions and polynomial approximations.
  • Knowledge of L'Hospital's rule for evaluating indeterminate forms.
  • Basic calculus concepts, including exponential functions and logarithms.
NEXT STEPS
  • Study the application of Taylor expansions for functions near limits.
  • Learn how to apply L'Hospital's rule to resolve limits involving exponential functions.
  • Explore the properties of logarithmic functions and their use in limit evaluation.
  • Review examples of limits involving indeterminate forms and their resolutions.
USEFUL FOR

Students studying calculus, particularly those focusing on limits, Taylor expansions, and methods for evaluating complex limits. This discussion is beneficial for anyone needing clarification on limit proofs and alternative approaches in calculus.

georgetown13
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Homework Statement


Determine the limit and then prove your claim.

limx\rightarrow\infty (1+\frac{1}{x^2} }) x

Homework Equations



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

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

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 \delta, given \epsilon >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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georgetown13 said:

Homework Statement


Determine the limit and then prove your claim.

limx\rightarrow\infty (1+\frac{1}{x^2} }) x


Homework Equations



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

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

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 \delta, given \epsilon >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

y = \left( 1 + \frac 1 {x^2}\right)^x

and work with \ln(y) using L'Hospital's rule.
 

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