Understanding Riemann Sums: Solving Lf(P) and Uf(P) Correctly

In summary, when calculating Lf(P) and Uf(P), there can be different answers depending on the chosen partition (P) and function (f). However, for a given P and f, Lf(P) and Uf(P) are specific numbers and not "multivalued". Different choices of P can result in different answers.
  • #1
KataKoniK
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When calculating Lf(P) and Uf(P) there can be many different answers correct? Provided that you solved it properly.
 
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  • #2
KataKoniK said:
When calculating Lf(P) and Uf(P) there can be many different answers correct? Provided that you solved it properly.


What do you mean??Have you read you question after writing it,to see whether it makes any sense?If the superior Riemann sum is different from the inferior one,the definite integral does not exist.Period.Since they involve taking a limit,that is not multivalued.

Daniel.
 
  • #3
KataKoniK said:
When calculating Lf(P) and Uf(P) there can be many different answers correct? Provided that you solved it properly.

That's not a very well phrased question. If you are given a particular partition, P, and a function, f, the Lf(P) is the sum of "length of interval times least value of f in that interval" and is a specific number. There are not "many different answers". The same is true of Uf(P). In general, Lf(P)< Uf(P).

Of course, a different choice of P might result in different answers.
 
  • #4
Thanks for the replies. I was just looking over some examples. So, just say they give a P = {0, 2, 3, 4} etc. they say to choose a number in between for ie. 0 and 2, so 1/2 or 1/4 would be correct choices, which will also result in a diff ans if one chose 1/2 instead of 1/4. I'm just learning this stuff, so sorry if I wasn't clear enough.
 
  • #5
nm I got it!
 

1. What is a Riemann sum?

A Riemann sum is a method used in calculus to approximate the area under a curve by dividing it into smaller rectangles and adding up their areas.

2. How is a Riemann sum calculated?

A Riemann sum is calculated by multiplying the width of each rectangle by the height of the function at a specific point within that rectangle, and then adding up all of these products.

3. What is the purpose of using Riemann sums?

The purpose of using Riemann sums is to estimate the area under a curve when it is not possible to find the exact value using traditional methods. It is also used to introduce the concept of integration in calculus.

4. What is the difference between a left, right, and midpoint Riemann sum?

In a left Riemann sum, the height of each rectangle is determined by the function value at the left endpoint of the interval. In a right Riemann sum, the height of each rectangle is determined by the function value at the right endpoint of the interval. In a midpoint Riemann sum, the height of each rectangle is determined by the function value at the midpoint of the interval.

5. How does the number of rectangles used in a Riemann sum affect the accuracy of the approximation?

The more rectangles used in a Riemann sum, the more accurate the approximation will be. As the number of rectangles approaches infinity, the Riemann sum will approach the actual area under the curve.

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