Integration on a open interval?

Click For Summary
Integrating a function over an open interval, such as (2,7), is conceptually similar to integrating over a closed interval, as the contributions from the endpoints are negligible. The discussion highlights that for most functions, including f(x) = x^2 + 2x + 3, the difference between open and closed intervals does not affect the integral's value. Concerns arise primarily with functions that have singularities or discontinuities at the endpoints, where limits may need to be considered. The conversation also clarifies that the integration of distributions, like delta functions, differs from standard functions. Overall, for typical functions, integrating over an open interval is straightforward and yields the same result as a closed interval.
GreenPrint
Messages
1,186
Reaction score
0

Homework Statement



I was wondering how one integrates on a open interval. For example let's say I wanted to integrate the function f(x) = x^2 + 2x + 3 on (2,7). Note that it's on the OPEN INTERVAL not closed of all the x values from 2 to 7 not including 2 to 7. I'm not trying to integrate on [2,7] but on (2,7). How do I do this? Thanks. Any ideas or suggestions or anything at all would be appreciated.

Homework Equations





The Attempt at a Solution

 
Physics news on Phys.org
It doesn't make any difference. Why do you think it does? The contribution from the endpoints is zero.
 
I know it may not make a difference for this function but what about functions whose anti derivatives are different if you were to take the left hand limit of the anti derivative and the right hand limit of the derivative at the points that were to determine the open interval
 
GreenPrint said:
I know it may not make a difference for this function but what about functions whose anti derivatives are different if you were to take the left hand limit of the anti derivative and the right hand limit of the derivative at the points that were to determine the open interval

The only way the contribution from a single point can make a difference is if you are integrating distributions with singularities. Like delta functions. Distributions are different from functions. Are you integrating distributions?
 
Question: A clock's minute hand has length 4 and its hour hand has length 3. What is the distance between the tips at the moment when it is increasing most rapidly?(Putnam Exam Question) Answer: Making assumption that both the hands moves at constant angular velocities, the answer is ## \sqrt{7} .## But don't you think this assumption is somewhat doubtful and wrong?

Similar threads

  • · Replies 15 ·
Replies
15
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 9 ·
Replies
9
Views
2K
Replies
4
Views
2K
  • · Replies 8 ·
Replies
8
Views
3K
  • · Replies 2 ·
Replies
2
Views
1K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 13 ·
Replies
13
Views
3K
Replies
32
Views
3K
  • · Replies 4 ·
Replies
4
Views
1K