Calculus AB : Integrating

Study concepts, example questions & explanations for Calculus AB

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Example Questions

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Example Question #1 : Use Riemann Sums

Let .

A relative maximum of the graph of   can be located at:

Possible Answers:

The graph of  has no relative maximum.

Correct answer:

Explanation:

At a relative minimum  of the graph , it will hold that  and 

First, find . Using the sum rule,

Differentiate the individual terms using the Constant Multiple and Power Rules:

Set this equal to 0:

Either:

, in which case, ; this equation has no real solutions.

 has two real solutions,  and 

Now take the second derivative, again using the sum rule:

Differentiate the individual terms using the Constant Multiple and Power Rules:

Substitute  for :

Therefore,  has a relative minimum at .

Now. substitute  for :

Therefore,  has a relative maximum at .

Example Question #2 : Use Riemann Sums

Estimate the integral of  from 0 to 3 using left-Riemann sum and 6 rectangles. Use 

Possible Answers:

Correct answer:

Explanation:

Because our  is constant, the left Riemann sum will be

Example Question #3 : Use Riemann Sums

Use Left Riemann sums with 4 subintervals to approximate the area between the x-axis, , and .

Possible Answers:

Correct answer:

Explanation:

To use left Riemann sums, we need to use the following formula:

.

where  is the number of subintervals, (4 in our problem),

 is the "counter" that denotes which subinterval we are working with,(4 subintervals mean that  will be 1, 2, 3, and then 4)

 is the function value when you plug in the "i-th" x value, (i-th in this case will be 1-st, 2-nd, 3-rd, and 4-th)

, is the width of each subinterval, which we will determine shortly.

and  means add all  versions together (for us that means add up 4 versions).

 

This fancy equation approximates using boxes. We can rewrite this fancy equation by writing , 4 times; 1 time each for , and . This gives us

Think of  as the base of each box, and  as the height of the 1st box.

This is basically , 4 times, and then added together.

Now we need to determine what  and  are.

To find  we find the total length between the beginning and ending x values, which are given in the problem as  and . We then split this total length into 4 pieces, since we are told to use 4 subintervals.

In short, 

Now we need to find the x values that are the left endpoints of each of the 4 subintervals. Left endpoints because we are doing Left Riemann sums.

The left most x value happens to be the smaller of the overall endpoints given in the question. In other words, since we only care about the area from  to , we'll just use the smaller one, , for our first .

Now we know that .

To find the next endpoint, , just increase the first x by the length of the subinterval, which is . In other words

Add the  again to get 

And repeat to find 

Now that we have all the pieces, we can plug them in.

 

 

plug each value into  and then simplify.

This is the final answer, which is an approximation of the area under the function.

Example Question #4 : Use Riemann Sums

The function  has the following values on the interval :

Approximate the integral of  on this interval using right Riemann sums.

Possible Answers:

Correct answer:

Explanation:

A Riemann sum integral approximation over an interval  with  subintervals follows the form:

It is essentially a sum of  rectangles, each with a base of length:  and variable heights: , which depend on the function value at .

In our case, we have function values over an interval:

Although the total interval has a length of .

Notice the points are equidistant. This distance is our subinterval  and since we are using the right point of each interval, we disregard the first function value:

Example Question #5 : Use Riemann Sums

Approximate 

Using a right Riemann sum, if  has the values:

Possible Answers:

Correct answer:

Explanation:

A Riemann sum integral approximation over an interval  with  subintervals follows the form:

It is essentially a sum of  rectangles, each with a base of length:  and variable heights: , which depend on the function value at .

In our case, we have function values over an interval:

Although the total interval has a length of  notice the points are equidistant. This distance is our subinterval: . Since we are using the right point of each interval, we disregard the first function value:

Example Question #6 : Use Riemann Sums

Approximate 

Using a right Riemann sum, if  has the values:

Possible Answers:

Correct answer:

Explanation:

A Riemann sum integral approximation over an interval  with  subintervals follows the form:

It is essentially a sum of  rectangles, each with a base of length:  and variable heights: , which depend on the function value at .

In our case, we have function values over an interval:

Although the total interval has a length of  notice the points are equidistant, with  intervals between. Each equidistant interval has length: 5

Since we are using the right point of each interval, we disregard the first function value:

Example Question #7 : Use Riemann Sums

Approximate 

Using a right Riemann sum, if  has the values:

Possible Answers:

Correct answer:

Explanation:

A Riemann sum integral approximation over an interval  with  subintervals follows the form:

It is essentially a sum of  rectangles, each with a base of length:  and variable heights: , which depend on the function value at .

In our case, we have function values over an interval:

Although the total interval has a length of  notice the points are equidistant, with  intervals between. Each equidistant interval has length: 5

Since we are using the right point of each interval, we disregard the first function value:

Example Question #8 : Use Riemann Sums

Approximate 

Using a right Riemann sum, if  has the values:

Possible Answers:

Correct answer:

Explanation:

A Riemann sum integral approximation over an interval  with  subintervals follows the form:

It is essentially a sum of  rectangles, each with a base of length:  and variable heights: , which depend on the function value at .

In our case, we have function values over an interval:

Although the total interval has a length of  notice the points are equidistant, with  intervals between. Each equidistant interval has length: . Since we are using the right point of each interval, we disregard the first function value:

Example Question #9 : Use Riemann Sums

The function  has the following values on the interval :

Approximate the integral of  on this interval using right Riemann sums.

Possible Answers:

Correct answer:

Explanation:

A Riemann sum integral approximation over an interval  with  subintervals follows the form:

It is essentially a sum of  rectangles, each with a base of length:  and variable heights: , which depend on the function value at .

In our case, we have function values over an interval:

Although the total interval has a length of .

Notice the points are equidistant, with  intervals between them. Each equidistance interval has length: . Since we are using the right point of each interval, we disregard the first function value:

Example Question #10 : Use Riemann Sums

Approximate 

Using a right Riemann sum, if  has the values:

Possible Answers:

Correct answer:

Explanation:

A Riemann sum integral approximation over an interval  with  subintervals follows the form:

It is essentially a sum of  rectangles, each with a base of length:  and variable heights: , which depend on the function value at .

In our case, we have function values over an interval:

Although the total interval has a length of  notice the points are equidistant, with  intervals between. Each equidistant interval has length: . Since we are using the right point of each interval, we disregard the first function value:

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