Solving L'Hôpital's Rule Homework: Find the Limit

In summary, the conversation is about finding the limit of a given function using L'Hôpital's rule. The participant attempted to solve it using the rule twice, but there was an error in the calculation. The correct solution is given as -0.35, and the participant asks for clarification on their mistake.
  • #1
LizzieL
12
0

Homework Statement



I have

[tex] L = \lim_{x\rightarrow 0} \Big( {\frac{\cos(1.92x)-1} {e^{2.33x} - 1 -2.33x}} \Big)[/tex]

I'm meant to use L'Hôpital's rule finding the limit, maybe twice.

The Attempt at a Solution



So, there's clearly something I have misunderstood, and hoping you might tell me what it is.

"Solution":
[tex] L = \lim_{x\rightarrow 0} \Big( {\frac{(-sin 1.92x)1.92} {2.33e^{2.33x}-2.33}}\Big)[/tex]

Getting rid of "1.92" gives

[tex] \lim_{x\rightarrow 0} \Big( {\frac{-sin1.92x} {1.21e^{2.33x}-1.21}}\Big) [/tex]
Then since [tex]{\frac {0} {0}}[/tex], I'll use the rule once more:

[tex] \lim_{x\rightarrow 0} {\frac{-cos 1.92x} {2.82e^{2.33x}}} = -0.35 [/tex]
What am I doing wrong?
 
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  • #2
there is 1.92 missing in the numerator.
 

1. What is L'Hôpital's Rule?

L'Hôpital's Rule is a mathematical tool used to evaluate limits of indeterminate forms, such as 0/0 or ∞/∞. It states that if the limit of a fraction f(x)/g(x) is an indeterminate form, then the limit of the ratio of the derivatives f'(x)/g'(x) will be equal to the original limit.

2. When should L'Hôpital's Rule be used?

L'Hôpital's Rule is most useful when evaluating limits involving fractions where both the numerator and denominator approach 0 or ∞. It can also be used to evaluate limits at infinity.

3. What are the steps for using L'Hôpital's Rule?

The first step is to identify the indeterminate form in the limit. Then, take the derivatives of the numerator and denominator separately. Next, plug the derivatives into the rule f'(x)/g'(x) and simplify. Finally, evaluate the limit using the new simplified fraction.

4. Are there any limitations to using L'Hôpital's Rule?

Yes, L'Hôpital's Rule can only be used when the limit is an indeterminate form. It cannot be used to evaluate limits where the numerator and denominator do not approach 0 or ∞, or when the limit is not an indeterminate form.

5. Can L'Hôpital's Rule be used for all types of functions?

L'Hôpital's Rule can be used for most types of functions, including polynomials, rational functions, and trigonometric functions. However, it cannot be used for functions with exponential growth, such as e^x, as the derivative of an exponential function is the same as the original function.

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