Calculus 2 : Derivatives

Study concepts, example questions & explanations for Calculus 2

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Example Questions

Example Question #36 : L'hospital's Rule

Evaluate the following limit:

Possible Answers:

Correct answer:

Explanation:

When evaluating the limit using normal methods (substitution), we receive the indeterminate form . When we receive the indeterminate form, we must use L'Hopital's Rule to evaluate the limit. The rule states that

Using the formula above for our limit, we get

The derivatives were found using the following rules:

Example Question #32 : L'hospital's Rule

Evaluate the limit:

Possible Answers:

Correct answer:

Explanation:

When evaluating the limit using normal methods (substitution), we get the indeterminate form . When this happens, to evaluate the limit we use L'Hopital's Rule, which states that

Using the above formula for our limit, we get

The derivatives were found using the following rule:

Example Question #31 : L'hospital's Rule

Evaluate the following limit, if possible:

Possible Answers:

The limit does not exist.

Correct answer:

Explanation:

To calculate the limit we first plug the limit value into the numerator and denominator of the expression. When we do this we get , which is undefined. We now use L'Hopital's rule which says that if  and  are differentiable and

,

then 

.

 

We are evaluating the limit

In this case we have 

 

and

 .

We differentiate both functions and find

  

and 

 

By L'Hopital's rule 

.

When we plug the limit value of 2 into this expression we get 9/3, which simplifies to 3.

Example Question #39 : L'hospital's Rule

Evaluate the following limit, if possible:

.

Possible Answers:

The limit does not exist.

Correct answer:

Explanation:

If we plugged in the limit value, , directly we would get the indeterminate value . We now use L'Hopital's rule which says that if  and  are differentiable and

,

then 

.

 

The limit we wish to evaluate is 

,

so in this case

and

.

We calculate the derivatives of both of these functions and find that

and

.

Thus

.

When we plug the limit value, , into this expression we get , which is .

Example Question #32 : L'hospital's Rule

Evaluate the following limit, if possible:

.

Possible Answers:

The limit does not exist

Correct answer:

The limit does not exist

Explanation:

We will show that the limit does not exist by showing that the limits from the left and right are different.

We will start with the limit from the right. Using the product rule we rewrite the limit

.

We know that

 

and 

so 

.

We calculate the limit from the left in the same way and find 

.

Thus the two-sided limit does not exist.

Example Question #41 : L'hospital's Rule

Evaluate the following limit, if possible:

.

Possible Answers:

The limit does not exist

Correct answer:

Explanation:

To calculate the limit we first plug the limit value into the numerator and denominator of the expression. When we do this we get , which is undefined. We now use L'Hopital's rule which says that if  and  are differentiable and

,

then 

.

 

In this case we are calculating 

so

and

.

We calculate the derivatives and find that 

and

.

Thus

.

Example Question #42 : L'hospital's Rule

Evaluate the following limit, if possible:

Possible Answers:

The limit does not exist

Correct answer:

The limit does not exist

Explanation:

The limit does not exist. When we first plug in the limit value, 0, we get 0/0 and indeterminate form. We may try to use L'Hopital's rule. However, we quickly discover that 

 

is not differentiable at x=0, so we cannot use L'Hopital's rule. We then consider the limits from the left and right. We determine that 

and

.

Thus the two sided limit does not exist.

Example Question #43 : L'hospital's Rule

Evaluate the following limit, if it exists:

Possible Answers:

Correct answer:

Explanation:

To calculate the limit we first plug the limit value into the numerator and denominator of the expression. When we do this we get , which is undefined. We now use L'Hopital's rule which says that if  and  are differentiable and

,

then 

.

 

We are trying to evaluate the limit

,

so we have

and

.

We differentiate both of these functions and find

and

.

Using L'Hopital's rule we see

.

Now when we plug the limit value into the expression we get , so 

.

Example Question #44 : L'hospital's Rule

Evaluate the following limit, if possible:

.

Possible Answers:

The limit does not exist.

Correct answer:

Explanation:

If we plugged in the limit value, , directly we would get the indeterminate value . We now use L'Hopital's rule which says that if  and  are differentiable and

,

then 

.

 

The limit we wish to evaluate is 

,

so we have

and

.

We evaluate the derivatives of these two functions and find

and

.

Thus, using L'Hopital's we find

.

However, when we plug the limit value into this second expression we still end up with the indeterminate value . So we use L'Hopital's again. 

and

.

Using L'Hopital's rule again we see

.

Plugging in the limit value now we see that the limit evaluates to 

Example Question #45 : L'hospital's Rule

Evaluate the following limit, if possible:

Possible Answers:

The limit does not exist

Correct answer:

Explanation:

To calculate the limit we first plug the limit value into the numerator and denominator of the expression. When we do this we get , which is undefined. We now use L'Hopital's rule which says that if  and  are differentiable and

,

then 

.

 

We are trying to evaluate the limit

so we have

and

.

We calculate the derivatives of these functions and get

and

.

Using L'Hopital's rule we find

.

Now when we plug in the limit value we get , so the limit evaluates to 0.

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