Understanding Riemann Sums

Oct 13, 2025 by wbrum.org 94 views

Introduction

In calculus, the Riemann sum is a method used to approximate the value of a definite integral. It is a fundamental concept in understanding the relationship between the area under a curve and the definite integral. In this article, we will explore how to calculate the right Riemann sum approximation for a given function using 5 subintervals.

Understanding Riemann Sums

A Riemann sum is an approximation of the area under a curve by dividing the area into small rectangles and summing the areas of the rectangles. The width of each rectangle is called the subinterval width, and the height of each rectangle is determined by the function value at a point within the subinterval.

Calculating the Riemann Sum

To calculate the right Riemann sum approximation for a given function, we need to follow these steps:

Divide the interval into subintervals: Divide the interval [3, 18] into 5 subintervals of equal width. The width of each subinterval is (18 - 3) / 5 = 3.
Determine the function values: Determine the function values at the right endpoint of each subinterval. The function values are given in the table below.

x	f(x)
3.6	2.5
6.6	4.2
9.6	6.1
12.6	7.5
15.6	8.9

Calculate the area of each rectangle: Calculate the area of each rectangle by multiplying the function value at the right endpoint of each subinterval by the width of the subinterval.
Sum the areas of the rectangles: Sum the areas of the rectangles to obtain the right Riemann sum approximation.

Calculating the Right Riemann Sum Approximation

Using the steps outlined above, we can calculate the right Riemann sum approximation for the given function.

x	f(x)	Area of Rectangle
3.6	2.5	2.5 * 3 = 7.5
6.6	4.2	4.2 * 3 = 12.6
9.6	6.1	6.1 * 3 = 18.3
12.6	7.5	7.5 * 3 = 22.5
15.6	8.9	8.9 * 3 = 26.7

The right Riemann sum approximation is the sum of the areas of the rectangles:

7.5 + 12.6 + 18.3 + 22.5 + 26.7 = 87.6

Conclusion

In this article, we have explored how to calculate the right Riemann sum approximation for a given function using 5 subintervals. We have outlined the steps to follow and provided a numerical example to illustrate the process. The right Riemann sum approximation is a useful tool for approximating the value of a definite integral, and it has many applications in calculus and other fields of mathematics.

References

[1] Riemann, B. (1854). Ueber die Darstellbarkeit einer Function durch eine trigonometrische Reihe. Göttinger Nachrichten, 13-23.
[2] Courant, R. (1937). Differential and Integral Calculus. New York: Interscience Publishers.

Introduction

In our previous article, we explored how to calculate the right Riemann sum approximation for a given function using 5 subintervals. In this article, we will answer some of the most frequently asked questions about Riemann sum approximation.

Q: What is the difference between left and right Riemann sum approximations?

A: The left and right Riemann sum approximations are two different methods of approximating the value of a definite integral. The left Riemann sum approximation uses the function values at the left endpoint of each subinterval, while the right Riemann sum approximation uses the function values at the right endpoint of each subinterval.

Q: How do I choose the number of subintervals for the Riemann sum approximation?

A: The number of subintervals for the Riemann sum approximation depends on the desired level of accuracy. A larger number of subintervals will result in a more accurate approximation, but it will also increase the computational effort.

Q: Can I use the Riemann sum approximation for functions that are not continuous?

A: The Riemann sum approximation is typically used for continuous functions. However, it can be extended to functions that are not continuous by using the concept of limits.

Q: How do I handle functions that have discontinuities within the interval?

A: When a function has a discontinuity within the interval, we can use the concept of limits to handle it. We can use the left and right limits to determine the function value at the point of discontinuity.

Q: Can I use the Riemann sum approximation for functions that are not defined at the endpoints of the interval?

A: Yes, we can use the Riemann sum approximation for functions that are not defined at the endpoints of the interval. We can simply ignore the function values at the endpoints and use the function values at the interior points.

Q: How do I determine the width of each subinterval?

A: The width of each subinterval is determined by dividing the length of the interval by the number of subintervals.

Q: Can I use the Riemann sum approximation for functions that are defined on a non-uniform interval?

A: Yes, we can use the Riemann sum approximation for functions that are defined on a non-uniform interval. We can simply divide the interval into subintervals of varying widths and use the function values at the right endpoint of each subinterval.

Q: How do I handle functions that have singularities within the interval?

A: When a function has a singularity within the interval, we can use the concept of limits to handle it. We can use the left and right limits to determine the function value at the point of singularity.

Conclusion

In this article, we have answered some of the most frequently asked questions about Riemann sum approximation. We have discussed the differences between left and right Riemann sum approximations, how to choose the number of subintervals, and how to handle functions that are not continuous or defined at the endpoints of the interval.

References

[1] Riemann, B. (1854). Ueber die Darstellbarkeit einer Function durch eine trigonometrische Reihe. Göttinger Nachrichten, 13-23.
[2] Courant, R. (1937). Differential and Integral Calculus. New York: Interscience Publishers.