Need helping evaluating this limit by expressing it as a definite integral

In summary, the problem is to evaluate a limit by expressing it as a definite interval integral. The given limit is represented as a Riemann sum and can be rewritten in the form of a definite interval integral. The key is to recognize that \frac{1}{n+i} can be expressed as \frac{1}{n}\frac{1}{1+\frac{i}{n}}. Using this, the limit can be evaluated by finding the appropriate values for Δx, f(x_{i}), and x_{i}*.
  • #1
skyturnred
118
0

Homework Statement



Evaluate the limit by expressing it as a definite [STRIKE]interval[/STRIKE] integral

[itex]\frac{lim}{n \rightarrow \infty}[/itex] ([itex]\frac{1}{n+1}[/itex]+[itex]\frac{1}{n+2}[/itex]+...+[itex]\frac{1}{n+(n-1)}[/itex]+[itex]\frac{1}{n+n}[/itex]

Homework Equations





The Attempt at a Solution



OK, so I know it has to do with Rieman sums. So I know I have to express it as

lim n->∞ [itex]\sum[/itex][itex]^{n}[/itex][itex]_{i=1}[/itex]f(x[itex]_{i*}[/itex])Δx

So I was able to change the original question into the following form:

lim n->∞ [itex]\sum[/itex][itex]^{n}[/itex][itex]_{i=1}[/itex][itex]\frac{1}{n+i}[/itex]

But I cannot find something that I can take out of that as Δx, nor can I find a way to find a or b to plug into the formula Δx=[itex]\frac{b-a}{n}[/itex]. Also, for the same reason, I cannot find f(x[itex]_{i}[/itex]*) or x[itex]_{i}[/itex]*. Can anyone help? Thanks!
 
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  • #2
Maybe write

[tex]\frac{1}{n+i}=\frac{1}{n}\frac{1}{1+\frac{i}{n}}[/tex]
 
  • #3
micromass said:
Maybe write

[tex]\frac{1}{n+i}=\frac{1}{n}\frac{1}{1+\frac{i}{n}}[/tex]

Thanks! I got it! Your response in combination with all the help you gave me yesterday definitely helped me understand Rieman sums!
 

FAQ: Need helping evaluating this limit by expressing it as a definite integral

What is a definite integral?

A definite integral is a mathematical concept used to calculate the area under a curve on a graph. It is represented by the symbol ∫ and has two limits, a lower limit and an upper limit, indicating the range of values to be integrated.

How is a definite integral related to limits?

A definite integral is closely related to limits because it is used to evaluate the limit of a function as the independent variable approaches a specific value. This is done by taking the definite integral of the function over a specific range of values and then evaluating the result at the desired limit point.

Can all limits be expressed as definite integrals?

No, not all limits can be expressed as definite integrals. Some limits may require different methods of evaluation, such as using L'Hopital's rule or manipulating the function algebraically.

What is the process for evaluating a limit by expressing it as a definite integral?

The process for evaluating a limit by expressing it as a definite integral involves finding the definite integral of the function over a specific range of values, evaluating the result at the limit point, and then taking the limit as the range of values approaches the limit point.

Are there any limitations to using definite integrals to evaluate limits?

Yes, there are limitations to using definite integrals to evaluate limits. Definite integrals can only be used for continuous functions, and sometimes the integral may be difficult or impossible to solve analytically. In these cases, numerical methods may be used to approximate the result.

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