Calculus 2 : Derivatives

Study concepts, example questions & explanations for Calculus 2

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Example Questions

Example Question #1651 : Calculus Ii

Euler's explicit method is often used to find a numerical solution to a differential equation.Given the step size and initial condition, it utilizes the tangent line equation to find the consecutive value of the solution function.

Find an approximation to a given differential equation using Euler's explicit method:

Use step size , and range of  from 0 to 3.

Initial condition is .

In the answer there should be three consecutive values of solution function for given range and step size of x.

Possible Answers:

Correct answer:

Explanation:

Recall formula of the tangent line to a two-dimensional function from Calculus 1:

For the Euler's method, this equation can be rewritten as:

Where  is the next value of the solution function,  is the derivative of the previous step. 

We are given a differential equation . Therefore, if we know the value of  and , we can find the . Consecutively, we can plug it into the Euler's method equation and find the .

Here is how this process is executed for the y(1):

1) Identify the initial condition and step size. This is the only information that Euler's method uses to calculate the approximation of solution function, other than the equation itself. In this case, we can say, that for the first step,

Note, that for the whole process, step size remains the same, 

2) Calculate the derivative of function at point  using given differential equation. In this case,

3) Note that in step 2 we found . Now we have all components to plug in to the Euler's method formula. Again, for our first step:

 

The same algorithm is used for y(2) and y(3). Note, that if we know step size and range of x, we will always know . For each consecutive step,  is the value of the solution function, found in the previous step.

Example Question #1 : Limits

Evaluate:

Possible Answers:

The limit does not exist.

Correct answer:

Explanation:

Let's examine the limit

first.

and 

,

 

so by L'Hospital's Rule, 

 

 

Since ,

 

Now, for each ; therefore, 

By the Squeeze Theorem, 

and 

Example Question #1 : L'hospital's Rule

Evaluate:

Possible Answers:

The limit does not exist.

Correct answer:

Explanation:

Therefore, by L'Hospital's Rule, we can find  by taking the derivatives of the expressions in both the numerator and the denominator:

 

Similarly, 

 

So 

But  for any , so 

Example Question #3 : Limits

Evaluate:

Possible Answers:

The limit does not exist.

Correct answer:

Explanation:

and 

Therefore, by L'Hospital's Rule, we can find  by taking the derivatives of the expressions in both the numerator and the denominator:

 

Similarly, 

 

so

 

Example Question #1 : L'hospital's Rule

Evaluate:

Possible Answers:

Correct answer:

Explanation:

and 

Therefore, by L'Hospital's Rule, we can find  by taking the derivatives of the expressions in both the numerator and the denominator:

 

 

 

Example Question #1 : L'hospital's Rule

Solve:  

Possible Answers:

Correct answer:

Explanation:

Substitution is invalid.  In order to solve , rewrite this as an equation.

Take the natural log of both sides to bring down the exponent.

Since  is in indeterminate form, , use the L'Hopital Rule.

L'Hopital Rule is as follows:

This indicates that the right hand side of the equation is zero.

Use the term  to eliminate the natural log.

 

Example Question #2 : L'hospital's Rule

Evaluate the limit using L'Hopital's Rule.

Possible Answers:

Undefined

Correct answer:

Explanation:

L'Hopital's Rule is used to evaluate complicated limits. The rule has you take the derivative of both the numerator and denominator individually to simplify the function. In the given function we take the derivatives the first time and get

This still cannot be evaluated properly, so we will take the derivative of both the top and bottom individually again. This time we get

.

Now we have only one x, so we can evaluate when x is infinity. Plug in infinity for x and we get

 and 

So we can simplify the function by remembering that any number divided by infinity gives you zero.

Example Question #5 : Euler's Method And L'hopital's Rule

Evaluate the limit using L'Hopital's Rule.

Possible Answers:

Undefined

Correct answer:

Explanation:

L'Hopital's Rule is used to evaluate complicated limits. The rule has you take the derivative of both the numerator and denominator individually to simplify the function. In the given function we take the derivatives the first time and get 

Since the first set of derivatives eliminates an x term, we can plug in zero for the x term that remains. We do this because the limit approaches zero.

This gives us

.

Example Question #3 : Euler's Method And L'hopital's Rule

Evaluate the limit using L'Hopital's Rule.

Possible Answers:

Undefined

Correct answer:

Explanation:

L'Hopital's Rule is used to evaluate complicated limits. The rule has you take the derivative of both the numerator and denominator individually to simplify the function. In the given function we take the derivatives the first time and get 

This still cannot be evaluated properly, so we will take the derivative of both the top and bottom individually again. This time we get

.

Now we have only one x, so we can evaluate when x is infinity. Plug in infinity for x and we get

Example Question #4 : Euler's Method And L'hopital's Rule

Calculate the following limit.

Possible Answers:

Correct answer:

Explanation:

To calculate the limit, often times we can just plug in the limit value into the expression. However, in this case if we were to do that we get , which is undefined.

What we can do to fix this is use L'Hopital's rule, which says

.

So, L'Hopital's rule allows us to take the derivative of both the top and the bottom and still obtain the same limit.

.

Plug in  to get an answer of .

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