Log in

View Full Version : Estimate the area under the graph of f(x) over [0, 1]..


Ali73
Jan 24, 2011, 02:35 PM
Use the following table of values to estimate the area under the graph of f(x) over [0, 1] by computing the average of R5 and L5.

x 0 0.2 0.4 0.6 0.8 1
f(x) 52 48 46 44 42 37

Ali73
Jan 24, 2011, 02:38 PM
Evaluate the limit.
lim(N--> Infinity) RN, f(x)=9x, [0,1]

Ali73
Jan 24, 2011, 03:04 PM
∫[0,4,|2x-4|,x]

Ali73
Jan 24, 2011, 03:06 PM
f(x) = x3 + 8

Ali73
Jan 24, 2011, 03:09 PM
Evaluate the indefinite integral
∫(8/x+8e^(x))*dx

Ali73
Jan 24, 2011, 03:12 PM
Find a formula for RN for the given function and interval. Then compute the area under the graph as a limit.
f(x) = x3 + 3x2, [0, 3]

ebaines
Jan 24, 2011, 03:24 PM
Do you mean this:


f(x) = x^3 + 3 x^2


You need to calculate the definite integral:


\displaystyle \int_0 ^3 (x^3 + 3x^2) dx


Do you know how to do that? I'm not sure what you mean by "RN" - please clarify.

Curlyben
Jan 24, 2011, 03:26 PM
Thank you for taking the time to copy your homework to AMHD.
Please refer to this announcement: https://www.askmehelpdesk.com/finance-accounting/announcement-font-color-ff0000-u-b-read-first-expectations-homework-help-board-b-u-font.html

liongal
Jan 24, 2011, 04:04 PM
LMAO... That's so funny, but I bet it was a homework q as well

jcaron2
Jan 24, 2011, 08:43 PM
I'm not familiar with the L5/R5 nomenclature either, but I think you're supposed to estimate the area under the curve by pretending that it's comprised of rectangles at the specified heights. I think the "L" and "R" mean "left" and "right", where the designation refers to whether the y-value forms the left or right corner of the rectangle. I'm not sure what the "5" means, other than the curve will be divided into five intervals (as specified by the six six points on the curve).

So in the "L" representation, for example, the first rectangle (from x=0 to x=0.2) would have a height of 52 (and therefore an area of 10.4) because its height is determined by the y-value on it's left, and the fifth rectangle (from x=0.8 to x=1) would have a height of 42 (area = 8.4). In the "R" representation, on the other hand, the first rectangle would have a height of 48 (area = 9.6), and the last would have a height of 37 (area = 7.4).

Neither the "L" or the "R" are very accurate at estimating the area. The "L" representation will tend to underestimate when the absolute value of the function is increasing (i.e. when the function is growing further from the x-axis in either the up or down direction as you move to the right), and overestimate when the absolute value is decreasing. The "R" version is just the opposite.

I think the problem is asking you to compute both the "L" and "R" estimates and average the two together (which should, indeed, be a better estimate than either one by itself). It's simply a matter of computing all five rectangular areas for each of the two representations (two of each of which are already done above), adding them up, and dividing by two.