I am selfstudying out of Calculus by Tom Apostol. As the title of this topic suggests, I am computing the area between two functions. Now I understand that this is simply the difference between integrals of the larger and smaller functions. For some reason, every single time I work through this problem I am left with only two of the three terms the book says are the answer. The problem is as follows:
Compute area A(S) between functions f(x) and g(x) within the given interval.
f(x) = x^1/3
g(x) = x^1/2
Interval is [0, 2]
So I integrate both functions and then find the difference between g(x) and f(x). Every time, I get the following answer:
4[sqr(2)]/3  3[cub(2)]/2
Now the book says the answer is:
4[sqr(2)]/3  3[cub(2)]/2 + 1/6
I cannot seem to find how the extra 1/6 was arrived at. I have worked through the problem numerous times, and I am obviously missing something. Anyone mind helping me out here?
Compute the area between two functions.
Page 1 of 17 Replies  679 Views  Last Post: 14 August 2011  06:38 PM
Replies To: Compute the area between two functions.
#2
Re: Compute the area between two functions.
Posted 14 August 2011  05:37 PM
I am actually going to try and scan in my work on the problem, as this might make it easier to determine where I went wrong. One second.
#3
Re: Compute the area between two functions.
Posted 14 August 2011  05:38 PM
I ran that integral on Wolfram, my TI89 and by hand. The only way the 1/6 could be included is if there was more to the problem. Perhaps there was more in the instructions?
#4
Re: Compute the area between two functions.
Posted 14 August 2011  05:48 PM
Thank you for your response. I'll get right back to you, going to read through the instructions once more.
#5
Re: Compute the area between two functions.
Posted 14 August 2011  06:12 PM
Alright attached are the problem and answer pages from the book. I had to throw them in a .zip folder because DIC wouldn't let me upload .xps files (Windows Document Writer). I appreciate the help, I am not sure what I am missing. The problem I am working on is problem 7.
Attached File(s)

Calculus problem.zip (424.69K)
Number of downloads: 54
#6
Re: Compute the area between two functions.
Posted 14 August 2011  06:23 PM
I got the same answer as you did originally, and the same answer Wolfram got. I would shoot your instructor an email asking about it. I have to disagree with the answer your book provided. Sometimes when you get second order differential equations, and you have to integrate two equations, you sometimes get a constant tagged on at the end of the final answer. However, I'm not seeing anything here that would account for the 1/6.
#7
Re: Compute the area between two functions.
Posted 14 August 2011  06:36 PM
I appreciate the help macosx, and I wish I had an instructor to email. I am starting school as a transfer student this upcoming spring, and I will be taking my first Calculus course. I have been selfstudying in the mean time so that the material is not new. There are a couple problems that are similar to this, where the answer has a constant thrown on the end. I will have to ask my professor once I am there.
#8
Re: Compute the area between two functions.
Posted 14 August 2011  06:38 PM
I would just skip over these problems, then. I think your instructor will come to the same conclusion we did, my TI89 did, and Wolfram did.
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