Series Expansion & l'Hopital's rule

In summary, the conversation discusses the topic of finding a suitable series expansion to the 4th degree of x using l'hopital's rule. The participants also mention using the Maclaurin series for e^x and e^-x in order to solve the problem.
  • #1
stuart4512
3
0
I'm preparing for my exam and have stumbled across this question. I understand how to execute the l'hopital's rule part of this but I just can't get there. I have no idea how to approach this in order to get a suitable series expansion to the 4th degree of x.

View attachment 3664

Thank you
 

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  • #2
stuart4512 said:
I'm preparing for my exam and have stumbled across this question. I understand how to execute the l'hopital's rule part of this but I just can't get there. I have no idea how to approach this in order to get a suitable series expansion to the 4th degree of x.

http://mathhelpboards.com/attachments/calculus-10/3664-series-expansion-amp-lhopitals-rule-2012b3-png

Thank you
For i) you just state the definition of coth(x).

For ii) you need to find the Maclaurin series for e^{x} and e^{-x}.
then plug those expansions into the coth(x) formula.

-Dan
 

FAQ: Series Expansion & l'Hopital's rule

What is a series expansion?

A series expansion is a mathematical technique used to approximate a function by expressing it as an infinite sum of simpler functions. It is particularly useful for calculating values of functions that cannot be easily evaluated by other methods.

How is a series expansion used in calculus?

In calculus, series expansions are used to approximate the behavior of a function near a specific point. This allows us to find the derivatives and integrals of the function at that point, as well as other important properties such as convergence and divergence of the function.

What is l'Hopital's rule and how is it related to series expansion?

L'Hopital's rule is a mathematical theorem that states that under certain conditions, the limit of a quotient of two functions is equal to the limit of the quotient of their derivatives. It is often used in conjunction with series expansion to evaluate indeterminate limits involving functions that cannot be easily evaluated directly.

What are the conditions for using l'Hopital's rule?

The two conditions for using l'Hopital's rule are that the functions involved must be differentiable and that the limit of the quotient of their derivatives must exist. In addition, the limit of the original function must be of the form 0/0 or ∞/∞.

Can l'Hopital's rule be used for any indeterminate form?

No, l'Hopital's rule can only be used for the indeterminate forms 0/0 and ∞/∞. It cannot be used for other indeterminate forms such as 1^∞ or ∞ - ∞, as these do not satisfy the conditions for the rule to be applied.

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