Finding a definite integral from the Riemann sum

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SUMMARY

The discussion centers on finding a definite integral using the Riemann sum method with the interval defined by a = 1 and b = 2. The user initially struggles with the expression involving logarithmic properties but ultimately simplifies the argument of the logarithm to derive the function f(x) = xlnx. This simplification is crucial for accurately calculating the definite integral. The final expression indicates a clear understanding of the relationship between Riemann sums and integrals.

PREREQUISITES
  • Understanding of Riemann sums
  • Familiarity with logarithmic properties
  • Basic knowledge of calculus, particularly definite integrals
  • Ability to manipulate algebraic expressions
NEXT STEPS
  • Study the derivation of definite integrals from Riemann sums
  • Learn about the properties of logarithmic functions
  • Explore the application of the Fundamental Theorem of Calculus
  • Practice problems involving integration of functions like f(x) = xlnx
USEFUL FOR

Students and educators in calculus, mathematicians interested in integral calculus, and anyone looking to deepen their understanding of Riemann sums and their applications in finding definite integrals.

crememars
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Homework Statement
Consider the following limit of a Riemann sum for a function f on [a, b]. Identify f, a, and b,
and express the limit as a definite integral.

*see actual expression in the description below. it was too complicated to type out so I included a picture instead.
Relevant Equations
∆x = (b-a)/n
xiR = a + i∆x
1679251462458.png


Hi! I am having trouble finalizing this problem.

The interval is given so we know that a = 1 and b = 2. From there you can figure out that ∆x = 1/n, xiR = 1 + i/n.
Using logarithmic properties, I rearranged the expression and wrote (1 + i/n)(1/n)ln[(n + i)/n].
I can guess that the function is going to look something like this: f(x) = xln(...) but I don't know what goes in the logarithmic function...

I have been trying to rewrite it in terms of xiR but no luck :(
any help would be really appreciated. thank you !
 
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Can you simplify the argument of the logarithm any further?
 
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pasmith said:
Can you simplify the argument of the logarithm any further?
Yes, I realized I was overcomplicating things. If I simplify (n+i)/n to (n/n +i/n) to (1+ i/n), I get f(x) = xlnx
 

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