Prove increasing function defines everywhere is Rinemann-integrable

In summary, the conversation discusses proving the Riemann integrability of a function f:R-->R that is increasing for any interval [a,b]. The person mentions knowing the proof of this fact from a book and suggests using the fact that an increasing function has a countable number of discontinuities. They also mention using the fact that a function is Riemann integrable if it is continuous almost everywhere. The other person confirms that this approach will work and mentions having proven the theorem before in a previous homework sheet.
  • #1
quasar987
Science Advisor
Homework Helper
Gold Member
4,807
32

Homework Statement


This is probably easy but i can't seem to see how to make it work right now.

I am trying to show that if we have a function f:R-->R that is increasing, then for any interval [a,b], it is riemann-integrable.

I know it's true because a book I saw refers to another book for the proof that an increasing fct as a countable number of discontinuities.


The Attempt at a Solution

 
Physics news on Phys.org
  • #2
If you know the proof of the fact that f is Riemann integrable iff it is continuous (lambda) almost everywhere then try to work it in...countable sets have 0 measure, of course.

Ie, suppose f is discontinuous on some non-null set and derive a contradiction.
 
  • #3
Is this just an idea you're throwing at me, or do you know for a fact that it works?

(As a matter of fact, I have proven that very theorem in an earlier homework sheet for this course)
 
  • #4
It will work. Try it :smile:
 

1. What does it mean for a function to be increasing?

An increasing function is a mathematical concept that describes a function whose output values increase as the input values increase. In other words, as the input increases, the output also increases. Graphically, this is represented by a line that slopes upwards from left to right.

2. What is the definition of Riemann-integrability?

Riemann-integrability is a mathematical concept that describes the ability to calculate the area under a curve using a method called the Riemann sum. It is a way to find the exact value of a definite integral, which represents the net area between the curve and the x-axis.

3. How do you prove that an increasing function is Riemann-integrable everywhere?

In order to prove that an increasing function is Riemann-integrable everywhere, you must show that it meets the criteria for Riemann-integrability. This includes being bounded on a closed interval, having a finite number of discontinuities, and having a limit at each point in the interval. If the function meets all of these conditions, then it is Riemann-integrable everywhere.

4. Can an increasing function be non-Riemann-integrable?

Yes, it is possible for an increasing function to be non-Riemann-integrable. This can occur if the function is not bounded on a closed interval or has an infinite number of discontinuities within the interval. In these cases, the Riemann sum cannot be used to accurately calculate the area under the curve, and the function is considered non-Riemann-integrable.

5. Why is it important for a function to be Riemann-integrable?

Riemann-integrability is important because it allows us to accurately calculate the area under a curve, which has many real-world applications in fields such as physics, economics, and engineering. It also allows us to solve certain types of differential equations and make predictions about the behavior of a system over time. Additionally, Riemann-integrability is a fundamental concept in calculus and serves as the basis for more advanced integration techniques.

Similar threads

  • Calculus and Beyond Homework Help
Replies
3
Views
264
  • Calculus and Beyond Homework Help
Replies
1
Views
495
  • Calculus and Beyond Homework Help
Replies
11
Views
1K
Replies
7
Views
1K
  • Calculus and Beyond Homework Help
Replies
3
Views
1K
  • Calculus and Beyond Homework Help
Replies
4
Views
902
  • Calculus and Beyond Homework Help
Replies
1
Views
569
  • Calculus and Beyond Homework Help
Replies
3
Views
802
  • Calculus and Beyond Homework Help
Replies
2
Views
830
Replies
9
Views
2K
Back
Top