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Math Help - Please help explain definite integrals and Riemann Sums, I am so confused

  1. #1
    Junior Member
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    Nov 2009
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    Please help explain definite integrals and Riemann Sums, I am so confused

    My professor has not answered any of my emails regarding definite integrals. Can anyone please explain this problem and solution?

    I am not sure how to put the actual formula in here but this is what I have:

    Consider the function f(x)= ((x^2/2)+7)
    Calculate Rn for f(x)=((x^2/2)+7) on the interval [0,3] and write your answer as a function of n without any summation signs.
    Rn=______
    lim Rn=______

    I know that the limit is 25.5 (found on another site) but I am so confused on how to actually solve it, the answer doesn't help.

    I think Xi is 3n/n and the change in X is 3/n

    But I have no idea where to go from there.

    Can anyone please help explain what to do?
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  2. #2
    Member
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    Do you know what a Riemann sum is ? If, so just think of a definite integral as another way of compute the Riemann sum over some interval fairly easier than just adding the term of a Riemann sum to however many sub-divisions over some interval.

    Here is a link that can explain better than I can:
    Pauls Online Notes : Calculus I - Definition of the Definite Integral

    Also for a bit help your definite integral based on the information given

    Edit: Are you writing the Riemann sum of this function? or definite integral? It seems to me, I might have misread, you are trying to write this in terms of n in the form of a definite integral, then you start to mention, the change and x and such.
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