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Example Questions
Example Question #1 : How To Find Midpoint Riemann Sums
Estimate the area under the curve for the following function using a midpoint Riemann sum from   to Â
 with Â
.
If we want to estimate the area under the curve from   to Â
 and are told to use Â
, Â this means we estimate the area using two rectangles that will each be two units wide and whose height is the value of the function at the midpoint of the interval. We have a rectangle from Â
 to Â
, Â whose height is the value of the function at Â
, Â and a rectangle from Â
 to Â
, Â whose height is the value of the function at Â
. Â First we can find the value of the function at these midpoints, and then add the areas of the two rectangles, which gives us the following:
Example Question #2 : How To Find Midpoint Riemann Sums
Estimate the area under the curve for the following function from   to Â
 using a midpoint Riemann sum with Â
 rectangles:
If we are told to use  rectangles from Â
 to Â
, Â this means we have a rectangle from Â
 to Â
, Â a rectangle from Â
 to Â
, Â a rectangle from Â
 to Â
, Â and a rectangle from Â
 to Â
. Â We can see that the width of each rectangle is Â
 because we have an interval that is Â
 units long for which we are using Â
 rectangles to estimate the area under the curve. The height of each rectangle is the value of the function at the midpoint for its interval, so first we find the height of each rectangle and then add together their areas to find our answer:
Example Question #2 : How To Find Midpoint Riemann Sums
Find the area under  on the intervalÂ
 using five midpoint Riemann sums.
The problem becomes this:
Addings these rectangles up to approximate the area under the curve is
Example Question #4 : How To Find Midpoint Riemann Sums
Approximate the area under the curve from  using the midpoint Riemann Sum with a partition of size five given the graph of the function.
Â
We begin by finding the given change in x:Â
We then define our partition intervals:
We then choose the midpoint in each interval:
Then we find the value of the function at the point. Â This is determined through observation of the graph
Then we simply substitute these values into the formula for the Riemann Sum
Example Question #3 : How To Find Midpoint Riemann Sums
Approximate the area underneath the given curve using the Riemann Sum with eight intervals for .
We begin by defining the size of our partitions and the partitions themselves.
We then choose the midpoint in each interval:
Then we find the function value at each point.
We then substitute these values into the Riemann Sum formula.
Example Question #1 : Midpoint Riemann Sums
Using a midpoint Reimann sum with , estimate the area under the curve from
 to
 for the following function:
Thus, our intervals are  toÂ
,Â
 toÂ
, andÂ
 toÂ
.
The midpoints of each interval are, respectively, ,Â
, andÂ
.
Next, we evaluate the function at each midpoint.
Finally, we calculate the estimated area using these values andÂ
Example Question #7 : How To Find Midpoint Riemann Sums
The table above gives the values for a function at certain points.
Using the data from the table, find the midpoint Riemann sum of  withÂ
, fromÂ
 toÂ
.
Thus, our intervals are  toÂ
,Â
 toÂ
, andÂ
 toÂ
.
The midpoints of each interval are, respectively, ,Â
, andÂ
.
Next, use the data table to take the values the function at each midpoint.
Â
Finally, we calculate the estimated area using these values and .
Example Question #1 : Differential Functions
Solve the integral
using the midpoint Riemann sum approximation with  subintervals. Â
Â
Midpoint Riemann sum approximations are solved using the formula
where  is the number of subintervals and
 is the function evaluated at the midpoint.
For this problem, . Â
The approximate value at each midpoint is below.
The sum of all the approximate midpoints values is , therefore
Example Question #2 : Functions
Solve the integral
using the midpoint Riemann sum approximation with  subintervals. Â
Midpoint Riemann sum approximations are solved using the formula
where  is the number of subintervals and
 is the function evaluated at the midpoint.
For this problem, . Â
The approximate value at each midpoint is below.
The sum of all the approximate midpoints values is , therefore
Example Question #1 : How To Find Midpoint Riemann Sums
Solve the integral
using the midpoint Riemann sum approximation with  subintervals. Â
1
1
Â
Midpoint Riemann sum approximations are solved using the formula
where  is the number of subintervals and
 is the function evaluated at the midpoint.
For this problem, . Â
The approximate value at each midpoint is below.
The sum of all the approximate midpoints values is , therefore
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